Cytokines and atherosclerosis: a comprehensive review of studies in mice

Proinflammatory cytokines in heart failure: double-edged swords

Increased circulating and intracardiac levels of proinflammatory cytokines have been associated with chronic heart failure. Following an initial insult, the increased production of proinflammatory cytokines, including TNF-α, IL-6, IL-1, and IL-18, jeopardizes the surrounding tissue through propagation of the inflammatory response and direct effects on the cardiac myocyte structure and function. Cardiac myocyte hypertrophy, contractile dysfunction, cardiac myocyte apoptosis, and extracellular matrix remodeling contribute enormously to the development and progression of chronic heart failure. Despite the identification of efficacious pharmacological regimens and introduction of mechanical interventions, chronic heart failure remains among the leading causes of mortality worldwide. To introduce novel therapeutic strategies that modulate the inflammatory response in the context of the failing heart, it is of prime importance to determine the contributions of TNF-α, IL-6, IL-1, and IL-18 in mediating cardiac adaptive and maladaptive responses, as well as delineating their downstream intracellular signaling pathways and their potential therapeutic implications.

αMβ₂ integrin activation prevents alternative activation of human and murine macrophages and impedes foam cell formation

RATIONALE

The alternative activation of monocytes by interleukin (IL)-13 and IL-4 is a significant component of the inflammatory response. The consequences of alternative activation in inflammatory diseases remain to be determined.

OBJECTIVE

In this report, we explored how integrins, receptors important for monocyte migration to inflammatory sites, regulate IL-13-mediated monocyte activation. We focused on the analysis of 2 proteins, which are upregulated during the alternative activation and are important for the development of atherosclerosis, an oxidative enzyme 15-lipoxygenase (15-LO) and a scavenger receptor CD36.

METHODS AND RESULTS

We found that adhesion of resting monocytes through β(2) integrins and inside-out activation of β(2) integrins by monocyte chemoattractant protein-1 did not change IL-13-stimulated 15-LO upregulation; however, preincubation of monocytes with the antibody MEM48, which generates full activation of β(2) integrins, significantly inhibited 15-LO mRNA and protein expression. In contrast, activation of β(1) integrins had no effect on 15-LO expression. Analysis of integrin clustering through α(M), α(L), α(X), and α(D) subunits demonstrated the pivotal role for integrin α(M)β(2) in inhibiting 15-LO expression. IL-13 treatment upregulates 15-LO-dependent CD36 expression on human monocytes; our studies showed that β(2) integrin activation and α(M) integrin clustering significantly inhibited IL-13-dependent CD36 mRNA and protein expression, as well as CD36-related foam cell formation. Moreover, IL-13 stimulation of α(M)-deficient peritoneal macrophages demonstrated an upregulated level of 15-LO induction, CD36 expression, and lipid accumulation as compared with wild-type controls.

CONCLUSIONS

The adhesion of monocytes/macrophages through activated integrin α(M)β(2) has a regulatory and potential atheroprotective function during the alternative activation of macrophages.

Reduced atherosclerosis and inflammatory cytokines in apolipoprotein-E-deficient mice lacking bone marrow-derived interleukin-1α

OBJECTIVE

Interleukin (IL)-1α and IL-1β are products of macrophages, endothelial cells and vascular smooth muscle cells; moreover, each of these cell types is affected by the pro-inflammatory properties of both IL-1's. Whereas several studies demonstrate the proatherogenic properties of IL-1β, the role of IL-1α in atherogenesis remains unclear. We assessed whether IL-1α and IL-1β from tissue resident vascular cells or emigrating bone marrow-derived cells promote the development of atherosclerosis in apoE-/- mice and determined the effect of selective macrophage IL-1α or IL-1β deficiency on degradation of LDL and cytokine production.

METHODS

We generated strains of double knock-out (KO) mice (apoE-/-/IL-1α-/- and apoE-/-/IL-1β-/-) and created chimeras consisting of apoE-/- mice reconstituted with bone marrow-derived cells from apoE-/-/IL-1+/+, apoE-/-/IL-1α-/- and apoE-/-/IL-1β-/-.

RESULTS

The areas of aortic sinus lesions were lower in either double KO mice compared to solely apoE-/- mice, despite higher non-HDL cholesterol levels. Importantly, selective deficiency of IL-1α or IL-1β in bone marrow-derived cells inhibited atherogenesis to the same extent as in double KO mice without affecting plasma lipids. Aortic sinus lesions in apoE-/- mice transplanted with IL-1β-/- or IL-1α-/- cells were 32% and 52% lower, respectively, than in IL-1+/+ transplanted mice. Ex vivo, isolated IL-1α-/- macrophages from atherosclerotic mice degraded LDL and secreted IL-6, TNFα and IL-12 similarly to IL-1+/+ macrophages; however, IL-1α deficient macrophages secreted reduced levels of IL-1β (-50%) and 2-3-fold higher levels of the anti-inflammatory cytokine IL-10.

CONCLUSION

We show for the first time that it is IL-1α from bone marrow-derived cells that accelerates atherogenesis in apoE-deficient mice rather than constitutive IL-1α in vascular cells, possibly by increasing the inflammatory cytokine profile of macrophages.

The versatility of HDL: a crucial anti-inflammatory regulator

BACKGROUND

Low levels of plasma high-density lipoprotein (HDL) represent a major cardiovascular risk factor and therefore raising HDL has been proposed to positively affect patients with atherosclerotic heart disease. However, the current evidence that raising HDL per se will reduce atherosclerosis and thereby cardiovascular events still remains controversial.

AIMS

In this review, we discuss the diverse anti-atherogenic and anti-inflammatory properties of HDL in the light of recent findings indicating that the quality rather than the mere quantity of HDL determines its beneficial effects against atherosclerosis. More specifically, we will focus on the conspicuous anti-inflammatory properties of HDL as this might contribute to the overall beneficial effects of HDL in diseased patients such as modulation of costimulatory/adhesion molecule expression, cytokine production and inhibition of the prototypical proinflammatory transcription factor NF-κB.

RESULTS

A range of clinical disorders share permanent inflammation as a characteristic hallmark including coronary artery disease, chronic kidney disease, diabetes mellitus or rheumatoid arthritis and also display distinct qualitative changes in the HDL compartment. Loss of anti-inflammatory functions of HDL is emerging as an important risk factor for disease progression and survival in these clinical entities.

CONCLUSIONS

It will be important to define the anti-inflammatory effects of HDL at the molecular level and to dissect the manifold functional implications to develop both novel functional assays that enable meaningful outcome studies and foster new therapeutic concepts in patients with altered HDL function.

CD11c/CD18 expression is upregulated on blood monocytes during hypertriglyceridemia and enhances adhesion to vascular cell adhesion molecule-1

OBJECTIVE

Atherosclerosis is associated with monocyte adhesion to the arterial wall that involves integrin activation and emigration across inflamed endothelium. Involvement of β(2)-integrin CD11c/CD18 in atherogenesis was recently shown in dyslipidemic mice, which motivates our study of its inflammatory function during hypertriglyceridemia in humans.

METHODS AND RESULTS

Flow cytometry of blood from healthy subjects fed a standardized high-fat meal revealed that at 3.5 hours postprandial, monocyte CD11c surface expression was elevated, and the extent of upregulation correlated with blood triglycerides. Monocytes from postprandial blood exhibited an increased light scatter profile, which correlated with elevated CD11c expression and uptake of lipid particles. Purified monocytes internalized triglyceride-rich lipoproteins isolated from postprandial blood through low-density lipoprotein-receptor-related protein-1, and this also elicited CD11c upregulation. Laboratory-on-a-chip analysis of whole blood showed that monocyte arrest on a vascular cell adhesion molecule-1 (VCAM-1) substrate under shear flow was elevated at 3.5 hours and correlated with blood triglyceride and CD11c expression. At 7 hours postprandial, blood triglycerides decreased and monocyte CD11c expression and arrest on VCAM-1 returned to fasting levels.

CONCLUSIONS

During hypertriglyceridemia, monocytes internalize lipids, upregulate CD11c, and increase adhesion to VCAM-1. These data suggest that analysis of monocyte inflammation may provide an additional framework for evaluating individual susceptibility to cardiovascular disease.

IL-20: biological functions mediated through two types of receptor complexes

IL-20 was discovered 10 years ago as a new member of the IL-10 family of cytokines. IL-20 shares the highest amino-acid sequence identity with IL-10, IL-24 and IL-19. IL-20 is secreted by immune cells and activated epithelial cells like keratinocytes. A high expression of the corresponding IL-20 receptor chains is detected on epithelial cells. In terms of function, IL-20 might therefore mediate a crosstalk between epithelial cells and tissue-infiltrating immune cells under inflammatory conditions. Transgenic and knockout mouse models for some cytokines and receptors of the IL-10-type cytokines have provided new insights into the biology of this family. This review will focus on the biological functions of IL-20 and its receptors within the IL-10 cytokine network.

Relative roles of various efflux pathways in net cholesterol efflux from macrophage foam cells in atherosclerotic lesions

PURPOSE OF REVIEW

Cholesterol efflux mechanisms are essential for macrophage cholesterol homeostasis. HDL, an important cholesterol efflux acceptor, comprises a class of heterogeneous particles that induce cholesterol efflux via distinct pathways. This review focuses on the understanding of the different cholesterol efflux pathways and physiological acceptors involved, and their regulation in atherosclerotic lesions.

RECENT FINDINGS

The synergistic interactions of ATP-binding cassette transporters A1 and G1 as well as ATP-binding cassette transporter A1 and scavenger receptor class B type I are essential for cellular cholesterol efflux and the prevention of macrophage foam cell formation. However, the importance of aqueous diffusion should also not be underestimated. Significant progress has been made in understanding the mechanisms underlying ATP-binding cassette A1-mediated cholesterol efflux and regulation of its expression and trafficking. Conditions locally in the atherosclerotic lesion, for example, lipids, cytokines, oxidative stress, and hypoxia, as well as systemic factors, including inflammation and diabetes, critically influence the expression of cholesterol transporters on macrophage foam cells. Furthermore, HDL modification and remodeling in atherosclerosis, inflammation, and diabetes impairs its function as an acceptor for cellular cholesterol.

SUMMARY

Recent advances in the understanding of the regulation of cholesterol transporters and their acceptors in atherosclerotic lesions indicate that HDL-based therapies should aim to enhance the activity of cholesterol transporters and improve both the quantity and quality of HDL.

WIN55212-2 ameliorates atherosclerosis associated with suppression of pro-inflammatory responses in ApoE-knockout mice

The role of inflammation in all stages of atherosclerosis has been actively investigated, with an emphasis on the discovery of novel and innovative drugs for treatment and prevention. The anti-inflammatory and immunomodulatory capacity of cannabinoids are well established, and these agents have a broad therapeutic potential in various inflammatory diseases, including cardiovascular diseases. The aim of this study was to investigate the effect of WIN55212-2, a synthetic cannabinoid, on atherosclerosis using the apolipoprotein E-knockout (ApoE(-/-)) mouse on a cholate-containing high-fat diet. Our results showed that WIN55212-2 reduced the size of atherosclerotic lesions in the aorta root, and did not affect serum lipid levels significantly. Furthermore, alleviation of atherosclerosis by WIN55212-2 was associated with a smaller content of macrophages in plaque lesion as well as decreasing pro-inflammatory gene expression and NF-κB activation in aortic tissues. Oxidized LDL (ox-LDL) dramatically induced NF-κB activation, and enhanced pro-inflammatory mRNA and protein expression in peritoneal macrophages isolated from ApoE(-/-) mice. It is noteworthy that all of the above-mentioned effects of ox-LDL were attenuated by WIN55212-2. Moreover, WIN55212-2 also attenuated the inflammatory response that LPS induced. AM630, a cannabinoid receptor 2 (CB₂) special antagonist completely abolished the protective effects of WIN55212-2 both in vivo and in vitro. Our data provide strong evidence that WIN55212-2 can potentially inhibit atherosclerosis in ApoE(-/-) mice. Importantly, all the beneficial effects of WIN55212-2 in our model were closely associated with the suppression of pro-inflammatory responses and were mediated by the CB₂ receptor.

The expression of cytokines in the aqueous humor and serum during endotoxin-induced uveitis in C3H/HeN mice

PURPOSE

The cytokines present in the aqueous humor and serum of C3H/HeN mice with endotoxin-induced acute anterior uveitis were analyzed, and the potential role of the cytokines in the pathogenesis of the disease was investigated.

METHODS

One hundred and eighty C3H/HeN mice were divided into an experimental group (n=150) and a control group (n=30). The mice in the experimental group were footpad-injected with 200 microg Vibro cholerae endotoxin (classical biotype, serotype Ogawa). The mice were then executed 4 h, 8 h, 16 h, 24 h, and 48 h after the injection of endotoxin. Aqueous humor and peripheral blood samples were collected using a microinjector. Ten samples were pooled together for analysis and centrifuged at 705x g, at 4 degrees C, for 3 min. The supernatant was collected and stored at -80 degrees C. The concentrations of tumor necrosis factor-alpha (TNF-alpha), interleukin-1 (IL-1), interleukin-6 (IL-6), interleukin-10 (IL-10), and interferon-gamma (IFN-gamma) in the samples were measured using a Cytometric Bead Array (CBA).

RESULTS

Acute anterior uveitis was successfully induced in C3H/HeN mice. At roughly 16 h post-injection, the concentrations of both IL-1 and IL-6 reached peak levels, and were significantly different from the control group (p=0.001 and p=0.001, respectively). At 24 h post-injection, the concentrations of IFN-gamma and IL-10 in the aqueous humor reached peak levels, and were significantly different from the control group (p=0.022 and p=0.003). The concentrations of IFN-gamma in serum at 4 and 24 hours were significantly different from the control group (p=0.033 and p=0.032). The concentration of IL-10 in serum, at 24 h post-injection, was also found to be significantly different from the control group (p=0.003). The cytokine expression levels in the aqueous humor were consistent with what would be expected during the process of inflammation.

CONCLUSIONS

Both IL-1 and IL-6 appear to play an important role in acute anterior uveitis; furthermore, the severity of inflammation may be associated with the dynamic balance of IFN-gamma and IL-10. Our results suggest that the cytokine network might be a useful therapeutic target in the treatment of acute anterior uveitis.

EGb761 ameliorates the formation of foam cells by regulating the expression of SR-A and ABCA1: role of haem oxygenase-1

AIMS

Accumulation of foam cells in the intima is a hallmark of early-stage atherosclerotic lesions. Ginkgo biloba extract (EGb761) has been reported to exert anti-oxidative and anti-inflammatory properties in atherosclerosis, yet the significance and the molecular mechanisms of action of EGb761 in the formation of macrophage foam cells are not fully understood.

METHODS AND RESULTS

Treatment with EGb761 resulted in a dose-dependent decrease in oxidized low-density lipoprotein (oxLDL)-mediated cholesterol accumulation in macrophages, a consequence that was due to a decrease in cholesterol uptake and an increase in cholesterol efflux. Additionally, EGb761 significantly down-regulated the mRNA and protein expression of class A scavenger receptor (SR-A) by decreasing expression of activator protein 1 (AP-1); however, EGb761 increased the protein stability of ATP-binding cassette transporter A1 (ABCA1) by reducing calpain activity without affecting ABCA1 mRNA expression. Small interfering RNA (siRNA) targeting haem oxygenase-1 (HO-1) abolished the EGb761-induced protective effects on the expression of AP-1, SR-A, ABCA1, and calpain activity. Accordingly, EGb761-mediated suppression of lipid accumulation in foam cells was also abrogated by HO-1 siRNA. Moreover, the lesion size of atherosclerosis was smaller in EGb761-treated, apolipoprotein E-deficient mice compared with the vehicle-treated mice, and the expression of HO-1, SR-A, and ABCA1 in aortas was modulated similar to that observed in macrophages.

CONCLUSION

These findings suggest that EGb761 confers a protection from the formation of foam cells by a novel HO-1-dependent regulation of cholesterol homeostasis in macrophages.

Metabolomic analysis identifies inflammatory and noninflammatory metabolic effects of genetic modification in a mouse model of Crohn's disease

Interleukin-10 is an immunosuppressive cytokine involved in the regulation of gastrointestinal mucosal immunity toward intestinal microbiota. Interleukin-10-deficient (IL10(-/-)) mice develop Crohn's disease-like colitis unless raised in germ-free conditions. Previous gas chromatography-mass spectrometry (GC-MS) metabolomic analysis revealed urinary metabolite differences between IL10(-/-) and wildtype C57BL/6 mice. To determine which of these differences were specifically associated with intestinal inflammation arising from IL10-deficiency, urine samples from IL10(-/-) and wildtype mice, housed in either conventional or specific pathogen-free conditions, were subjected to GC-MS metabolomic analysis. Fifteen metabolite differences, including fucose, xanthurenic acid, and 5-aminovaleric acid, were associated with intestinal inflammation. Elevated urinary levels of xanthurenic acid in IL10(-/-) mice were attributed to increased production of kynurenine metabolites that may induce T-cell tolerance toward intestinal microbiota. Liquid chromatography-mass spectrometry analysis confirmed that plasma levels of kynurenine and 3-hydroxykynurenine were elevated in IL10(-/-) mice. Eleven metabolite differences, including glutaric acid, 2-hydroxyglutaric acid, and 2-hydroxyadipic acid, were unaffected by the severity of inflammation. These metabolite differences may be associated with residual genes from the embryonic stem cells of the 129P2 mouse strain that were used to create the IL10(-/-) mouse, or may indicate novel functions of IL10 unrelated to inflammation.

Increased aortic atherosclerotic plaque development in female apolipoprotein E-null mice is associated with elevated thromboxane A2 and decreased prostacyclin production

The production of thromboxane A(2) (TXA(2)) and prostacyclin (prostaglandin I(2), PGI(2)) is known to be increased in patients with atherosclerosis. In this study, we evaluated the influence of gender on TXA(2) and PGI(2) production, and their association with the progression of atherosclerosis in apolipoprotein E-null (ApoE(-/-)) mice maintained on a high fat diet for 3 months. En face analyses of aortas showed marked increases in plaque formation in female ApoE(-/-) mice. Quantification of the hematoxylin/eosin (H&E) stained cross sections of the aortic arch revealed 3 to 4-fold higher plaque thickness in female ApoE(-/-) mice. Analyses of 24-hours urine samples for 11-dehydro TXB(2) and 2, 3-dinor-6-keto PGF(1a) indicated that female ApoE(-/-) mice produce up to 15-fold more TXA(2) and 50% less PGI(2) than the age matched males. Interestingly, the serum cholesterol levels in ApoE(-/-) females were 20% lower than males on the high fat regimen. No gender-associated changes in the number of T lymphocytes, mast cells and macrophages were evident in the lesion areas of ApoE(-/-) mice. The results suggest that the markedly elevated TXA(2) production and reduced PGI(2) production are gender-related proatherogenic risk factors in female ApoE(-/-) mice.

Angiotensin-converting enzyme inhibition down-regulates the pro-atherogenic chemokine receptor 9 (CCR9)-chemokine ligand 25 (CCL25) axis

Many experimental and clinical studies suggest a relationship between enhanced angiotensin II release by the angiotensin-converting enzyme (ACE) and the pathophysiology of atherosclerosis. The atherosclerosis-enhancing effects of angiotensin II are complex and incompletely understood. To identify anti-atherogenic target genes, we performed microarray gene expression profiling of the aorta during atherosclerosis prevention with the ACE inhibitor, captopril. Atherosclerosis-prone apolipoprotein E (apoE)-deficient mice were used as a model to decipher susceptible genes regulated during atherosclerosis prevention with captopril. Microarray gene expression profiling and immunohistology revealed that captopril treatment for 7 months strongly decreased the recruitment of pro-atherogenic immune cells into the aorta. Captopril-mediated inhibition of plaque-infiltrating immune cells involved down-regulation of the C-C chemokine receptor 9 (CCR9). Reduced cell migration correlated with decreased numbers of aorta-resident cells expressing the CCR9-specific chemoattractant factor, chemokine ligand 25 (CCL25). The CCL25-CCR9 axis was pro-atherogenic, because inhibition of CCR9 by RNA interference in hematopoietic progenitors of apoE-deficient mice significantly retarded the development of atherosclerosis. Analysis of coronary artery biopsy specimens of patients with coronary artery atherosclerosis undergoing bypass surgery also showed strong infiltrates of CCR9-positive cells in atherosclerotic lesions. Thus, the C-C chemokine receptor, CCR9, exerts a significant role in atherosclerosis.

Immunotherapy for the Prevention of Myointimal Hyperplasia After Experimental Balloon Injury of the Rat Carotid Artery

We assessed the effect of novel immunotherapeutic heat-killed bacterial (Actinomycetales) preparations on the development of myointimal hyperplasia (MIH) in a rat carotid balloon trauma model and the effect on the immune response by measuring the expression of interferon γ (IFN-γ; (Th1) and interleukin 4 (IL-4; Th2). There was a significant reduction (P < .001) in intima/media ratios (mean ± SEM) in the rats treated by immunomodulation (0.52 ± 0.03 Gordonia bronchialis, 0.60 ± 0.03 Rhodococcus coprophilus, 0.43 ± 0.03 Tsukamurella inchonensis, 0.37 ± 0.03 Mycobacterium vaccae), in comparison with untreated controls (0.91 ± 0.05). Postballoon trauma G bronchialis increased messenger RNA (mRNA) IFN-γ (P < .02) and reduced mRNA IL-4 (P < .05). R coprophilus, T inchonensis, and M vaccae significantly increased production of mRNA IFN-γ (P < .001). R coprophilus and M vaccae also decreased production of mRNA IL-4 (P < .05, P < .01). Treatment with heat-killed Actinomycetales inhibits MIH through a combination of enhanced Th1 and attenuated Th2 response. Immunomodulation may provide a novel therapeutic option to prevent restenosis.

NF kappaB activation in embryonic endothelial progenitor cells enhances neovascularization via PSGL-1 mediated recruitment: novel role for LL37

Embryonal endothelial progenitor cells (eEPCs) are capable of inducing therapeutic angiogenesis in a chronic hind limb model. However, the proportion of eEPCs recruited to the ischemic tissue appears to be a limiting step for the induction of cell-based therapeutic neovascularization. In the present study, we primed eEPCs with the human cathelicidin LL37 (hCAP-18) ex vivo to selectively enhance the eEPC-dependent gain of perfusion in vivo and elucidated the mechanism of action of LL37 on eEPCs. Seven days after femoral artery excision, 5 x 10(6) eEPCs (wt, wild type; p65t, transiently p65 transient; p65s, stable p65-transfected; LL37-eEPCs, LL37 peptide preincubated) were retroinfused into the anterior tibial vein. Recruitment of diI-labeled eEPCs in the ischemic gastrocnemic muscle was investigated 2 days later, whereas collateral growth and perfusion score (obtained by fluorescent microspheres) were assessed at day 7 and day 35 and are given as percentage of day 7 level. Capillary/muscle fiber ratio in the ischemic lower limb was obtained at day 35. Embryonic EPC recruitment in vitro and in vivo was found elevated after LL37 and p65t pretreatment, but not in p65s-eEPCs displaying increased IkappaBalpha or after LL37 in IkappaB-DN overexpressing eEPCs. Using LL37- and p65t-eEPCs, collateral growth (181 +/- 10% and 165 +/- 8%, respectively) surpassed that of wt-eEPCs (135 +/- 7%), increasing perfusion ratio (208 +/- 20% and 210 +/- 17% vs. 142 +/- 12% in wt-eEPCs, respectively), whereas p65s-eEPCs exerted no additive effect (collateral growth 130 +/- 8%; perfusion ratio 155 +/- 15%). Moreover, p65t-eEPC-induced neovascularization was abrogated by blocking antibodies against E-selectin and P-selectin glycoprotein ligand-1 (PSGL-1). We conclude that NF kappaB activation by LL37 or transient p65-transfection increases functionally relevant eEPC recruitment to ischemic muscle tissue via induction of PSGL-1 and E-selectin.

The Constitutive Function of Native TRPC3 Channels Modulates Vascular Cell Adhesion Molecule-1 Expression in Coronary Endothelial Cells Through Nuclear Factor κB Signaling

Rationale : Upregulation of endothelial vascular cell adhesion molecule (VCAM)-1 and the subsequent increase in monocyte recruitment constitute critical events in atherogenesis. We have recently shown that in human coronary artery endothelial cells (HCAECs) regulated expression of VCAM-1 depends, to a significant extent, on expression and function of the Ca 2+ -permeable channel transient receptor potential canonical (TRPC)3, regardless of the ability of the stimulatory signal to induce regulated Ca 2+ influx, leading to the hypothesis that TRPC3 constitutive, rather than regulated function, contributes to the underlying signaling mechanism.

Objective : The present studies addressed this important question and gathered mechanistic insight on the signaling coupling constitutive TRPC3 function to VCAM-1 expression.

Methods and Results : In HCAECs, maneuvers that prevent Ca 2+ influx or knockdown of TRPC3 markedly reduced tumor necrosis factor (TNF)α-induced VCAM-1 and monocyte adhesion. TNFα also induced TRPC3 expression and TRPC3-mediated constitutive cation influx and currents. Stable (HEK293 cells) or transient (HCAECs) overexpression of TRPC3 enhanced TNFα-induced VCAM-1 compared to wild-type cells. IκBα phosphorylation/degradation was reduced by TRPC3 knockdown and increased by channel overexpression. Inhibition of calmodulin completely prevented nuclear factor κB activation, whereas blocking calmodulin-dependent kinases or NADPH oxidases rendered partial inhibition.

Conclusions : Our findings indicate that in HCAECs expression of VCAM-1 and monocyte adhesion depend, to a significant extent, on TRPC3 constitutive function through a signaling mechanism that requires constitutive TRPC3-mediated Ca 2+ influx for proper activation of nuclear factor κB, presumably through Ca 2+ -dependent activation of the calmodulin/calmodulin-dependent kinase axis.

ATP-binding membrane cassette transporter A1 (ABCA1): a possible link between inflammation and reverse cholesterol transport

Atherosclerosis is characterized by a chronic inflammatory condition that involves numerous cellular and molecular inflammatory components. A wide array of inflammatory mediators, such as cytokines and proteins produced by macrophages and other cells, play a critical role in the development and progression of the disease. ATP-binding membrane cassette transporter A1 (ABCA1) is crucial for cellular cholesterol efflux and reverse cholesterol transport (RCT) and is also identified as an important target in antiatherosclerosis treatment. Evidence from several recent studies indicates that inflammation, along with other atherogenic-related mediators, plays distinct regulating roles in ABCA1 expression. Proatherogenic cytokines such as interferon (IFN)-γ and interleukin (IL)-1β have been shown to inhibit the expression of ABCA1, while antiatherogenic cytokines, including IL-10 and transforming growth factor (TGF)-β1, have been shown to promote the expression of ABCA1. Moreover, some cytokines such as tumor necrosis factor (TNF)-α seem to regulate ABCA1 expression in species-specific and dose-dependent manners. Inflammatory proteins such as C-reactive protein (CRP) and cyclooxygenase (COX)-2 are likely to inhibit ABCA1 expression during inflammation, and inflammation induced by lipopolysaccharide (LPS) was also found to block the expression of ABCA1. Interestingly, recent experiments revealed ABCA1 can function as an antiinflammatory receptor to suppress the expression of inflammatory factors, suggesting that ABCA1 may be the molecular basis for the interaction between inflammation and RCT. This review aims to summarize recent findings on the role of inflammatory cytokines, inflammatory proteins, inflammatory lipids, and the endotoxin-mediated inflammatory process in expression of ABCA1. Also covered is the current understanding of the function of ABCA1 in modulating the immune response and inflammation through its direct and indirect antiinflammatory mechanisms including lipid transport, high-density lipoprotein (HDL) formation and apoptosis.

Pathogen-mediated inflammatory atherosclerosis is mediated in part via Toll-like receptor 2-induced inflammatory responses

Studies in humans have established that polymorphisms in genes encoding the innate immune Toll-like receptors (TLRs) are associated with inflammatory atherosclerosis. In hyperlipidemic mice, TLR2 and TLR4 have been reported to contribute to atherosclerosis progression. Human and mouse studies support a role for the oral pathogen Porphyromonas gingivalis in atherosclerosis, although the mechanisms by which this pathogen stimulates inflammatory atherosclerosis via innate immune system activation is not known. Using a genetically defined apolipoprotein E-deficient (ApoE(-/-)) mouse model we demonstrate that pathogen-mediated inflammatory atherosclerosis occurs via both TLR2-dependent and TLR2-independent mechanisms. P. gingivalis infection in mice possessing functional TLR2 induced the accumulation of macrophages as well as inflammatory mediators including CD40, IFN-gamma and the pro-inflammatory cytokines IL-1 beta, IL-6 and tumor necrosis factor-alpha in atherosclerotic lesions. The expression of these inflammatory mediators was reduced in atherosclerotic lesions from P. gingivalis-infected TLR2-deficient (TLR2(-/-)) mice. These studies provide a mechanistic link between an innate immune receptor and pathogen-accelerated atherosclerosis by a clinically and biologically relevant bacterial pathogen.

Il-19 reduces VSMC activation by regulation of mRNA regulatory factor HuR and reduction of mRNA stability

While much is known about the deleterious effects of pro-inflammatory cytokines on development of vascular disease, little is reported on the direct effects of anti-inflammatory cytokines on the vascular smooth muscle cell (VSMC) response to injury. Interleukin-19 (IL-19) is a recently described Th2, anti-inflammatory interleukin. We have previously reported that IL-19 is absent in normal VSMC, but induced in VSMC by inflammatory cytokines and in arteries by injury. IL-19 is anti-proliferative for VSMC. The purpose of this study is to determine the molecular mechanism of these effects. In cultured, primary human VSMC, IL-19 reduces abundance of proliferative and inflammatory gene proteins and mRNA, including Cyclin D1, IL-1beta, IL-8, and COX2. IL-19 does not inhibit NF-kappaB, but does transiently reduce cytoplasmic abundance of the mRNA stability factor HuR. The mRNA stabilizing function of HuR is linked to its phosphorylation and cytoplasmic translocation. IL-19 reduces serine phosphorylation of HuR, and activation of PKCalpha, a known regulator of HuR translocation. Actinomycin D transcription blockade demonstrates that IL-19 treatment significantly reduces stability of proliferative and inflammatory mRNAs. Knock down of HuR with siRNA also reduces stability of these inflammatory mRNA transcripts. These data indicate that IL-19 has direct effects on VSMC mRNA stability. One potential mechanism whereby IL-19 reduces the VSMC response to injury is by regulation of HuR abundance and cytoplasmic translocation, with a subsequent decrease in mRNA half-life of proliferative and inflammatory mRNA transcripts.

Dual transfer of GFP gene and MGd into stem-progenitor cells: toward in vivo MRI of stem cell-mediated gene therapy of atherosclerosis

RATIONALE AND OBJECTIVES

The aim of this study was to develop a new technique, the use of magnetic resonance (MR) imaging (MRI) to monitor gene/MR-cotransferred stem-progenitor cells (SPCs) recruited to atherosclerosis.

MATERIALS AND METHODS

First, a green fluorescent protein (GFP) gene and a T1 MR contrast agent (motexafin gadolinium [MGd]) were cotransferred into neural or bone marrow (BM)-derived SPCs. GFP expression and MGd signal were confirmed by fluorescent microscopy and quantified by flow cytometry. Cell viability and proliferation were then evaluated by trypan blue exclusion and 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium assay, and GFP/MGd-transferred cells were imaged using 1.5-T and 9.4-T MR scanners. For in vivo validation, GFP/MGd-cotransferred beta-galactosidase-BM SPCs were transplanted to apolipoprotein E-knockout mice, and cell migration to atherosclerotic aortas was monitored using 9.4-T micro-MRI with subsequent histologic correlations.

RESULTS

Fluorescent microscopy demonstrated simultaneous GFP expression and MGd signals in cotransferred-cells. Quantitative flow cytometry showed GFP-positive cells at 47 +/- 25% and 56 +/- 12% and MGd-positive cells at 96 +/- 6% and 57 +/- 11% for neural stem cells and BM cells, respectively. Cell viability and metabolic rates of cotransferred cells were 86 +/- 4% and 84 +/- 12%, respectively. In vivo MRI revealed high MR signals of the aortic walls in GFP/MGd-transferred mice, which were confirmed by histologic correlations.

CONCLUSION

This study has initially proven the new concept of MRI for plaque-specific, cell-mediated gene expression of atherosclerosis.

Disturbances in some gene expression in T regulatory cells separated from children with metabolic syndrome

The metabolic syndrome (MS) is defined as a cluster of risk factors, including abdominal obesity, dyslipidaemia, glucose intolerance and hypertension, which increase the risk for coronary heart disease. The immunological aspects of obesity and MS, including the role of T regulatory cells, have been intensively investigated. The aim of this study was to determine whether there is any disturbance in T regulatory cells number and/or function in children with MS. The percentages of T regulatory cells in the peripheral blood of children fulfilling the International Diabetes Federation criteria of the disease (n = 47) were assessed. Treg cells were also separated for further analysis of multiple genes important in their function with the use of real-time RT-PCR. We did not observe any difference in Treg percentages between study and control group but there was lower expression of some molecules including transforming growth factor-beta and interleukin-12 family members in Treg cells separated from children with MS compared to the healthy subjects. Our study is the first to report significant disturbances in some gene expression in T regulatory cells separated from children with MS. The results should be useful for further research in this field, including immunotherapeutic interventions.

Erythropoietin suppresses the formation of macrophage foam cells: role of liver X receptor alpha

BACKGROUND

In addition to the hematopoietic effect of erythropoietin, increasing evidence suggests that erythropoietin also exerts protective effects for cardiovascular diseases. However, the role of erythropoietin and its underlying mechanism in macrophage foam cell formation are poorly understood.

METHODS AND RESULTS

Compared with wild-type specimens, erythropoietin was increased in atherosclerotic aortas of apolipoprotein E-deficient (apoE(-/-)) mice, mainly in the macrophage foam cells of the lesions. Erythropoietin levels in culture medium and macrophages were significantly elevated in response to oxidized low-density lipoprotein in a dose-dependent manner. Furthermore, erythropoietin markedly attenuated lipid accumulation in oxidized low-density lipoprotein-treated macrophages, a result that was due to an increase in cholesterol efflux. Erythropoietin treatment significantly increased ATP-binding cassette transporters (ABC) A1 and ABCG1 mRNA and protein levels without affecting protein expression of scavenger receptors, including scavenger receptor-A, CD36, and scavenger receptor-BI. The upregulation of ABCA1 and ABCG1 by erythropoietin resulted from liver X receptor alpha activation, which was confirmed by its prevention on expression of ABCA1 and ABCG1 after pharmacological or small interfering RNA inhibition of liver X receptor alpha. Moreover, the erythropoietin-mediated attenuation on lipid accumulation was abolished by such inhibition. Finally, reduced lipid accumulation and marked increase in ABCA1 and ABCG1 were demonstrated in erythropoietin-overexpressed macrophages.

CONCLUSIONS

Our data suggest that erythropoietin suppresses foam cell formation via the liver X receptor alpha-dependent upregulation of ABCA1 and ABCG1.

Metformin, an antidiabetic agent, suppresses the production of tumor necrosis factor and tissue factor by inhibiting early growth response factor-1 expression in human monocytes in vitro

Metformin, an antidiabetic agent, has been shown to reduce atherothrombotic disease in diabetic patients independent of antihyperglycemic effect. Recent studies have demonstrated that metformin attenuates the proinflammatory responses in human vascular wall cells and macrophages. However, the detailed molecular mechanisms underlying these therapeutic effects remain unclear. In the present study, we investigated the effects of metformin on tumor necrosis factor (TNF) production and tissue factor (TF) expression in isolated human monocytes stimulated with lipopolysaccharide (LPS) or oxidized low-density lipoprotein (oxLDL). Metformin significantly inhibited both TNF production and TF expression in isolated human monocytes stimulated with LPS or oxLDL. Metformin also significantly inhibited TNF and TF mRNA in human monocytes stimulated with LPS. Although metformin did not inhibit the activation of either nuclear factor-kappaB or activator protein-1, it inhibited the expression of early growth response factor-1 (Egr-1) and phosphorylation of extracellular signal-regulated protein kinase (ERK) 1/2 in monocytes stimulated with LPS or oxLDL. These results suggest that metformin may attenuate the inflammatory responses, at least in part, by suppressing the production of both TNF and TF through the inhibition of the ERK1/2-Egr-1 pathway in human monocytes.

Systemic levels of G-CSF and interleukin-6 determine the angiogenic potential of bone marrow resident monocytes

There is considerable interest in the potential of cell-based approaches to mediate therapeutic angiogenesis for acute and chronic vascular syndromes. Using a mouse model of HLI, we showed previously that adoptive transfer of a small number of donor monocytes enhanced revascularization significantly. Herein, we provide data suggesting that the BM resident monocytes sense systemic signals that influence their future functional capacity. Specifically, following induction of distant ischemia, the angiogenic capacity of BM resident monocytes is reduced markedly. We provide evidence that G-CSF and IL-6 represent such "conditioning" signals. Systemic levels of G-CSF and IL-6 are increased significantly following induction of HLI. Accordingly, BM resident monocytes from ischemic mice exhibited increased pSTAT3 and STAT3 target gene expression. Finally, G-CSFR(-/-) and IL-6(-/-) mice were resistant to the deleterious effects of ischemic conditioning on monocyte angiogenic potential. RNA expression profiling suggested that ischemia-conditioned monocytes in the BM up-regulate the well-described M2 polarization markers Chi3l4 and Lrg1. Consistent with this observation, M2-skewed monocytes from SHIP(-/-) mice also had impaired angiogenic capacity. Collectively, these data show that G-CSF and IL-6 provide signals that determine the angiogenic potential of BM resident monocytes.

Characterization of synergistic induction of CX3CL1/fractalkine by TNF-alpha and IFN-gamma in vascular endothelial cells: an essential role for TNF-alpha in post-transcriptional regulation of CX3CL1

CX3CL1/fractalkine, a chemokine specific to monocytes and NK cells, is induced synergistically by TNF-alpha and IFN-gamma in vascular endothelial cells. However, the mechanism for this synergism remains unclear. This study explored the hypothesis that the CX3CL1 expression is regulated at a posttranscriptional level, which may responsible for the synergism between TNF-alpha and IFN-gamma. Brief exposure of HUVECs to TNF-alpha led to a robust increase in IFN-gamma-induced CX3CL1 production. We found that TNF-alpha stabilized CX3CL1 mRNA in HUVECs stimulated with IFN-gamma. Cloning of 3' untranslated region (UTR) of CX3CL1 mRNA revealed the presence of a single copy of nonametric AU-rich element in its 3'UTR, and a luciferase reporter assay showed that a single AU-rich element is a crucial cis-element in the posttranscriptional regulation of CX3CL1. TNF-alpha treatment resulted in the phosphorylation of p38 MAPK and its downstream target, MAPK-activated protein kinase-2, but IFN-gamma did not affect the levels of MAPK and MAPK-activated protein kinase-2 phosphorylation induced by TNF-alpha. Treatment of the cells with an inhibitor of p38 MAPK accelerated the decay of CX3CL1 mRNA induced by TNF-alpha or the combination of TNF-alpha and IFN-gamma. Immunoprecipitation assay revealed that mRNA stabilizer HuR directly binds to 3'UTR of CX3CL1 mRNA. CX3CL1 expression is under control of posttranscriptional regulation, which is involved in the synergistic induction of CX3CL1 in response to the combined stimulation with TNF-alpha and IFN-gamma.

Expression of cytokine genes in the aorta is altered by the deficiency in MCP-1: effect of a high-fat, high-cholesterol diet

BACKGROUND

Monocyte chemoattractant protein-1 (MCP-1) facilitates the recruitment of monocytes/macrophages into vascular intima, and it is probably involved in the regulation of other signaling pathways relevant to the pathogenesis of arteriosclerosis and metabolic disturbances. However, chemokines are redundant. Consequently, the protective effect of MCP-1 deficiency may be mediated by changes in other cytokine signals.

METHODS AND RESULTS

Changes in the pattern of gene expression in the aorta were evaluated in LDLr(-/-) and MCP-1(-/-) LDLr(-/-) mice fed either chow or Western-style diet. Functional analyses were used to characterize the pathways affected and to identify biological processes in which MCP-1 may play an additional role. Some data also suggest that MCP-5 may act as a surrogate for MCP-1 deletion. Arteriosclerosis lesion and plaque composition are associated with enrichment in the cytokine-cytokine receptor interaction pathway.

CONCLUSIONS

There is a complex network of interactions linking MCP-1 and other cytokines. The lack of MCP-1 limits the aortic response to atherogenic stimuli, but does not completely protect against neointima formation. Activation of alternative inflammatory pathways in the vascular wall in response to MCP-1 deficiency should be considered to fully understand the actual role of this chemokine.

Studies on protective effects of human paraoxonases 1 and 3 on atherosclerosis in apolipoprotein E knockout mice

Paraoxonase (PON) possesses antiatherogenic potentials, but the distinct functions of PON members in alleviating atherosclerosis are not yet clear. This study aimed to evaluate the protective effects of hPON1 and hPON3 against atherosclerosis, and thereby exploring their synergistic mechanism in atherosclerosis development. We generated the recombinant adenovirus AdPON1 and AdPON3, which were capable of expressing hPON1 and hPON3. After AdPON1 and AdPON3 were injected intravenously into 5-week-old apolipoprotein E knockout mice, abundant hPON1 and hPON3 mRNA expression levels were detected. However, increase in serum lactonase activity was detected only in AdPON1-treated mice. Serum antioxidation and anti-inflammation capabilities in AdPON1-treated mice, reflected by malondialdehyde, total antioxidant capability and tumor necrosis factor-alpha levels, were greatly enhanced, whereas those in AdPON3-treated mice were not significantly affected. Nevertheless, histological analysis revealed that adenovirus-mediated expression of hPON1, hPON3 or both of them reduced atherosclerotic plaque area to a similar extent. Although no synergistic mechanism was detected in reducing arterial lesion size, hPON1 and hPON3 showed synergistic effects on promoting macrophage cholesterol efflux. In conclusion, hPON1 and hPON3 exhibited similar potentials in reducing arterial lesion size, but they exerted antiatherogenic effects in distinct ways.

Familial Mediterranean Fever as an Emerging Clinical Model of Atherogenesis Associated with Low-Grade Inflammation

Numerous inflammatory and innate immune pathways are involved in atherogenesis. Elaboration of clinical models of inflammation-induced atherogenesis may further advance our knowledge of multiple inflammatory pathways implicated in atherogenesis and provide a useful tool for cardiovascular prevention. Familial Mediterranean fever (FMF) is a chronic inflammatory disorder with profiles of inflammatory markers close to that seen in the general population. In a few recent studies, it has been shown that endothelial dysfunction, increased atherosclerotic burden and activation of platelets accompany attack-free periods of FMF. Colchicine is proved to be useful in suppression of inflammation in FMF. Preliminary basic and clinical studies suggest that this relatively safe drug may be useful for cardiovascular protection in patients with FMF and in the general population. Multinational prospective studies are warranted to further elaborate clinical model of inflammation-induced atherosclerosis associated with FMF.

Familial mediterranean Fever as an emerging clinical model of atherogenesis associated with low-grade inflammation

Numerous inflammatory and innate immune pathways are involved in atherogenesis. Elaboration of clinical models of inflammation-induced atherogenesis may further advance our knowledge of multiple inflammatory pathways implicated in atherogenesis and provide a useful tool for cardiovascular prevention. Familial Mediterranean fever (FMF) is a chronic inflammatory disorder with profiles of inflammatory markers close to that seen in the general population. In a few recent studies, it has been shown that endothelial dysfunction, increased atherosclerotic burden and activation of platelets accompany attack-free periods of FMF. Colchicine is proved to be useful in suppression of inflammation in FMF. Preliminary basic and clinical studies suggest that this relatively safe drug may be useful for cardiovascular protection in patients with FMF and in the general population. Multinational prospective studies are warranted to further elaborate clinical model of inflammation-induced atherosclerosis associated with FMF.

Lipoprotein (a) as an acute phase reactant in patients on chronic hemodialysis

Lipoprotein (a) [Lp(a)], is an independent risk factor for atherosclerotic cardiovascular disease in patients on chronic hemodialysis. A low concentration of high density lipoprotein cholesterol (HDL-C) and serum albumin are another potential risk factors. The purpose of this study was to explore in patients on chronic hemodialysis, whether Lp(a) elevated levels are influenced by activated acute phase response (APR) and the correlation of Lp(a) with HDL-C and serum albumin. In 69 hemodialysis patients with C-reactive protein (CRP) levels over than 10 mg/L and 101 hemodialysis patients with CRP levels in the normal range, Lp(a), HDL-C and serum albumin were determined in relation to CRP, as a sensitive marker of an APR. Results showed that serum concentration of CRP in 69 hemodialysis patients was significantly higher than in controls (44,62 mg/L versus 8,75 mg/L, p<0,01).Patients with elevated CRP had significantly higher serum levels of Lp(a) and lower serum levels of HDL-C and albumin, than patients with CRP in the normal range ( 35,39 mg/dl versus 28,6 mg/dl, p<0,01, 0,91 mmol/L versus 1,29 mmol/L, p<0,01 and 33,56 g/L versus 35,86 g/L, p<0,01). Lp(a) levels correlated positively with CRP and negatively with HDL-C and serum albumin, in patients with elevated CRP, but not in healthy controls. According to the results Lp(a) reacts as an acute phase protein, in patients with APR.

Th1/Th2 cytokine production by clove-treated mice

Although clove possesses several biological and therapeutic properties, its immunomodulatory action has not been fully investigated. The goal of this work was to investigate the effect of administration of the water extract of clove over a short-term to BALB/c mice on Th1 (IFN-gamma and IL-2) and Th2 (IL-4 and IL-10) cytokine production. After treatment, spleen cells were aseptically removed and cells were stimulated with concanavalin A. Supernatants of cell cultures were used for cytokine determination by ELISA. The chemical composition of the extract was also carried out, revealing that eugenol(4-allyl-2-methoxyphenol) was the major component in our sample. Although the anti-inflammatory action of clove has been mentioned, our data showed that clove administration to mice did not influence the Th1/Th2 cytokine balance. Further studies dealing with cytokine expression and production will provide a better understanding of clove's immunomodulatory and anti-inflammatory actions, using different extract concentrations and different intake periods.

Inactivation of the tumour suppressor, PTEN, in smooth muscle promotes a pro-inflammatory phenotype and enhances neointima formation

AIMS

Phosphatase and tensin homolog (PTEN) is implicated as a negative regulator of vascular smooth muscle cell (SMC) proliferation and injury-induced vascular remodelling. We tested if selective depletion of PTEN only in SMC is sufficient to promote SMC phenotypic modulation, cytokine production, and enhanced neointima formation.

METHODS AND RESULTS

Smooth muscle marker expression and induction of pro-inflammatory cytokines were compared in cultured SMC expressing control or PTEN-specific shRNA. Compared with controls, PTEN-deficient SMC exhibited increased phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt)/mammalian target of rapamycin (mTOR) signalling and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-kappaB) activity, reduced expression of SM markers (SM-alpha-actin and calponin), and increased production of stromal cell-derived factor-1alpha (SDF-1alpha), monocyte chemotactic protein-1 (MCP-1), interleukin-6 (IL-6), and chemokine (C-X-C motif) ligand 1 (KC/CXCL1) under basal conditions. PI3K/Akt or mTOR inhibition reversed repression of SM marker expression, whereas PI3K/Akt or NF-kappaB inhibition blocked cytokine induction mediated by PTEN depletion. Carotid ligation in mice with genetic reduction of PTEN specifically in SMC (SMC-specific PTEN heterozygotes) resulted in enhanced neointima formation, increased SMC hyperplasia, reduced SM-alpha-actin and calponin expression, and increased NF-kappaB and cytokine expression compared with wild-types. Lesion formation in SMC-specific heterozygotes was similar to lesion formation in global PTEN heterozygotes, indicating that inactivation of PTEN exclusively in SMC is sufficient to induce considerable increases in neointima formation.

CONCLUSION

PTEN activation specifically in SMC is a common upstream regulator of multiple downstream events involved in pathological vascular remodelling, including proliferation, de-differentiation, and production of multiple cytokines.

Beta2-Glycoprotein I is a Target of T Cell Reactivity in Patients with Advanced Carotid Atherosclerotic Plaques

Evidence in animal models that beta2-glycoprotein I (β2GPI), the principal target of autoimmune antiphospholipid antibodies, is involved in the initiation and progression of atherosclerosis, prompted us to investigate the possible role of this self protein as a target autoantigen of immune reactions in patients with carotid atherosclerosis. Plaque-infiltrating T lymphocytes from patients, and circulating T lymphocytes from patients and healthy subjects were tested by cell proliferation assay and by flow cytometry for intracellular cytokine expression in response to β2GPI. ELISA was used to detect cytokine production in culture supernatants and anti-β2GPI/anti-cardiolipin antibodies in serum samples. Eight of 35 PBMC samples and 1 of 5 plaque-infiltrating T lymphocyte samples from patients proliferated in response to β2GPI, whereas PBMC from healthy subjects did not. Patients' PBMC samples that proliferated in response to β2GPI produced significantly higher IFN-γ and TNF-α than non-proliferating PBMC. β2GPI-specific plaque-derived T lymphocytes expressed IFN-γ, TNF-α and IL-4, suggesting concomitant Th1 and Th2 activation. Only one patient's serum was positive for anti-β2GPI and anti-cardiolipin IgM antibodies. These new findings indicate that β2GPI induces a cellular immune response in a subpopulation of patients with carotid atherosclerosis thus contributing to the inflammatory responses involved in carotid atherosclerotic disease.

Systems biology approaches to the study of cardiovascular drugs

Atherogenic lipids and chronic inflammation drive the development of cardiovascular disorders such as atherosclerosis. Many cardiovascular drugs target the liver which is involved in the formation of lipid and inflammatory risk factors. With robust systems biology tools and comprehensive bioinformatical packages becoming available and affordable, the effect of novel treatment strategies can be analyzed more comprehensively and with higher sensitivity. For example, beneficial as well as adverse effects of drugs can already be detected on the gene and metabolite level, and prior to their macroscopic manifestation. This chapter describes a systems approach for a prototype CV drug with established beneficial and adverse effects. All relevant steps, for example, experimental design, tissue collection and high quality RNA preparation, bioinformatical analysis of functional processes, and pathways (targeted and untargeted) are addressed.

Cynical hostility and stimulated Th1 and Th2 cytokine production

Hostility has been associated with heightened proinflammatory activity. However, it is not known whether greater hostility contributes to greater inflammation by promoting higher Th1 activity, lower Th2 activity, or both. The present study examines the relation of hostility to mitogen-stimulated Th1 and Th2 cytokine production in vitro. Participants were 193 healthy men and women (mean age 37.3; 44% non-white). Hostility was assessed with a 20-item version of the Cook-Medley Hostility Scale (CMHS). PHA-stimulated interleukin (IL)-2, tumor necrosis factor (TNF)-alpha, and interferon (IFN)-gamma were used to measure Th1 activity; PHA-stimulated IL-4, IL-5, and IL-10 were used to measure Th2 activity. Greater hostility was related to greater production of two of the three Th1 cytokines, TNF-alpha and IFN-gamma. Hostility was not associated with any measure of Th2 cytokine production. Associations with Th1 cytokines were independent of age, sex, race, socioeconomic status, body mass index, depressive symptoms, and health-related behaviors, and were consistent across men and women. Associations were not explained by social network characteristics, social support, or personality traits closely associated with social behavior. Exploratory analyses substituting the CMHS cognitive, affective, and behavioral subscales for total hostility revealed that associations between hostility and Th1 cytokine production were primarily driven by the cognitive component of hostility (i.e., cynicism). Results suggest that a unique dimension of hostility, particularly the cynicism subcomponent, that is unrelated to social factors, may influence inflammation by promoting greater Th1 cytokine production. This effect on stimulated cytokine activity may have implications for a role of hostility in exacerbating immune-related disease.

Tumor necrosis factor-α signaling in macrophages

Tumor necrosis factor-α (TNFα) was cloned over 2 decades ago and its identification in part led to the discovery of a super family of tumor necrosis factors (TNFs) and their receptors. TNFα signals through two transmembrane receptors, TNFR1 and TNFR2, and regulates a number of critical cell functions including cell proliferation, survival, differentiation, and apoptosis. Macrophages are the major producers of TNFα and interestingly are also highly responsive to TNFα. Aberrant TNFα production and TNF receptor signaling have been associated with the pathogenesis of several diseases, including rheumatoid arthritis, Crohn's disease, atherosclerosis, psoriasis, sepsis, diabetes, and obesity. TNFα has been shown to play a pivotal role in orchestrating the cytokine cascade in many inflammatory diseases and because of this role as a "master-regulator" of inflammatory cytokine production, it has been proposed as a therapeutic target for a number of diseases. Indeed anti-TNFα drugs are now licensed for treating certain inflammatory diseases including rheumatoid arthritis and inflammatory bowel disease. In this review we discuss the discovery of TNFα and its actions especially in regulating macrophage biology. Given its importance in several human diseases, we also briefly discuss the role of anti-TNFα therapeutics in the treatment of inflammatory diseases.

Ubiquitin carboxyl terminal hydrolase L1 negatively regulates TNFalpha-mediated vascular smooth muscle cell proliferation via suppressing ERK activation

Deubiquitinating enzymes (DUBs) appear to be critical regulators of a multitude of processes such as proliferation, apoptosis, differentiation, and inflammation. We have recently demonstrated that a DUB of ubiquitin carboxyl terminal hydrolase L1 (UCH-L1) inhibits vascular lesion formation via suppressing inflammatory responses in vasculature. However, the precise underlying mechanism remains to be defined. Herein, we report that a posttranscriptional up-regulation of UCH-L1 provides a negative feedback to tumor necrosis factor alpha (TNFalpha)-mediated activation of extracellular signal-regulated kinases (ERK) and proliferation in vascular smooth muscle cells (VSMCs). In rat adult VSMCs, adenoviral over-expression of UCH-L1 inhibited TNFalpha-induced activation of ERK and DNA synthesis. In contrast, over-expression of UCH-L1 did not affect platelet derived growth factor (PDGF)-induced VSMC proliferation and activation of growth stimulating cascades including ERK. TNFalpha hardly altered UCH-L1 mRNA expression and stability; however, up-regulated UCH-L1 protein expression via increasing UCH-L1 translation. These results uncover a novel mechanism by which UCH-L1 suppresses vascular inflammation.

Cytokine production from peripheral blood mononuclear cells and polymorphonuclear leukocytes in patients studied for suspected obstructive sleep apnea

PURPOSE

The relationship between obstructive sleep apnea (OSA) and atherosclerosis-related inflammation has been poorly investigated, particularly focusing on functional responses of immune cells playing a key role in atherogenesis and in comparison with control groups with similar cardiovascular risk factors which are known to be themselves associated with inflammation. We sought to determine cellular tumor necrosis factor-alpha (TNF-α) production from peripheral blood mononuclear cells (PBMCs) and interleukin (IL)-8 release from neutrophils (PMNs) in patients studied for suspected OSA.

METHODS

Thirty-six consecutive patients who underwent a nocturnal complete cardiorespiratory evaluation for suspected OSA were initially evaluated. Serum, PBMCs, and PMNs were isolated (at baseline and after 12 weeks) from patients with apnea-ipopnea index (AHI) >20 (OSA group, n = 16) and from control patients with AHI <5 (nonOSA group, n = 11). All patients continued the same pharmacological therapy for 12 weeks; the OSA group was additionally treated with nocturnal continuous positive-airway-pressure ventilation (cPAP).

RESULTS

The two groups had similar clinical characteristics (prevalence of hypertension, dyslipidemia, diabetes, and cardio-metabolic therapies) except for obesity. Resting and stimulated TNF-α production from PBMCs and IL-8 release from PMNs were similar in the two groups. Serum cytokines resulted within the normal range. In the OSA group, cPAP was not associated with changes in cellular responses.

CONCLUSIONS

In patients showing similar prevalence of major cardiovascular risk factors and cardio-metabolic therapies, differing for the presence or absence of OSA, cytokine productions from PBMC and PMN were similar and were not modified during cPAP therapy. Studies designed to investigate OSA-associated inflammation should carefully match the control group subjects.

Is exercise training an effective therapy targeting endothelial dysfunction and vascular wall inflammation?

There is an increasing evidence that endothelial dysfunction and vascular wall inflammation are present in all stages of atherosclerosis. Atherosclerosis does not have to necessarily progress to an acute clinical event. Several therapeutic strategies exist, such as exercise training, which mitigates endothelial dysfunction and inflammation. Exercise training consistently improves the nitric oxide bioavailability, and the number of endothelial progenitor cells, and also diminishes the level of inflammatory markers, namely pro-inflammatory cytokines and C-reactive protein. However, the mechanisms by which exercise improves endothelial function in coronary artery disease patients are not fully clarified. Several mechanisms have been proposed to explain the positive effect of exercise on the disease progression. They include the decrease in cytokine production by the adipose tissue, skeletal muscles, endothelial cells, and blood mononuclear cells, and also, the increase in the bioavailability of nitric oxide, antioxidant defences, and regenerative capacity of endothelium. This study aims to provide a critical review of the literature linking exercise, inflammation, and endothelial dysfunction in coronary artery patients, and to discuss the potential mechanisms behind the exercise-training improvement of endothelial function and inflammatory status.

High-fat diet induces lung remodeling in ApoE-deficient mice: an association with an increase in circulatory and lung inflammatory factors

Hypercholesterolemia is increasingly considered the basis for not only cardiovascular pathologies but also several complications affecting other organs such as lungs. In this study, we examined the effect of hypercholesterolemia on lung integrity using a mouse model (ApoE(-/-)) of high-fat (HF) diet-induced atherosclerosis. A 12-week HF diet regimen induced systemic production of TNF-alpha, IFN-gamma, GMC-SF, RANTES, IL-1alpha, IL-2 and IL-12 with TNF-alpha as the predominant cytokine in ApoE(-/-) mice. Concomitantly, TNF-alpha, IFN-gamma and MIP-1alpha were detected in brochoalveolar lavage (BAL) fluids of these mice, coinciding with lung inflammation consisting primarily of monocytes/macrophages. Such lung inflammation correlated with marked collagen deposition and an increase in matrix metalloproteinase-9 activity in ApoE(-/-)mice without mucus production. Although TGF-beta1 was undetectable in the BAL fluid of ApoE(-/-) mice on HF diet, it showed a much wider tissue distribution compared with that of control animals. Direct exposure of smooth muscle cells to oxidized-LDL, in vitro, induced a time-dependent expression of TNF-alpha. Direct intratracheal TNF-alpha-administration induced a lung inflammation pattern in wild-type mice that was strikingly similar to that induced by HF diet in ApoE(-/-) mice. TNF-alpha administration induced expression of several factors known to be critically involved in lung remodeling, such as MCP-1, IL-1beta, TGF-beta1, adhesion molecules, collagen type-I and TNF-alpha itself in the lungs of treated mice. These results suggest that hypercholesterolemia may promote chronic inflammatory conditions in lungs that are conducive to lung remodeling potentially through TNF-alpha-mediated processes.

Berberine promotes the development of atherosclerosis and foam cell formation by inducing scavenger receptor A expression in macrophage

Berberine is identified to lower the serum cholesterol level in human and hamster through the induction of low density lipoproteins (LDL) receptor in hepatic cells. To evaluate its potential in preventing atherosclerosis, the effect of berberine on atherosclerosis development in apolipoprotein E-deficient (apoE(-/-)) mice was investigated. In apoE(-/-) mice, berberine induced in vivo foam cell formation and promoted atherosclerosis development. The foam cell formation induced by berberine was also observed in mouse RAW264.7 cells, as well as in mouse and human primary macrophages. By inducing scavenger receptor A (SR-A) expression in macrophages, berberine increased the uptake of modified LDL (DiO-Ac-LDL). Berberine-induced SR-A expression was also observed in macrophage foam cells in vivo and in the cells at atherosclerotic lesion. Analysis in RAW264.7 cells indicated that berberine induced SR-A expression by suppressing PTEN expression, which led to sustained Akt activation. Our results suggest that to evaluate the potential of a cholesterol-reducing compound in alleviating atherosclerosis, its effect on the cells involved in atherosclerosis development, such as macrophages, should also be considered. Promotion of foam cell formation could counter-balance the beneficial effect of lowering serum cholesterol.

Pleiotropic roles of S100A12 in coronary atherosclerotic plaque formation and rupture

Macrophages, cytokines, and matrix metalloproteinases (MMP) play important roles in atherogenesis. The Ca(2+)-binding protein S100A12 regulates monocyte migration and may contribute to atherosclerosis by inducing proinflammatory cytokines in macrophages. We found significantly higher S100A12 levels in sera from patients with coronary artery disease than controls and levels correlated positively with C-reactive protein. S100A12 was released into the coronary circulation from ruptured plaque in acute coronary syndrome, and after mechanical disruption by percutaneous coronary intervention in stable coronary artery disease. In contrast to earlier studies, S100A12 did not stimulate proinflammatory cytokine production by human monocytes or macrophages. Similarly, no induction of MMP genes was found in macrophages stimulated with S100A12. Because S100A12 binds Zn(2+), we studied some functional aspects that could modulate atherogenesis. S100A12 formed a hexamer in the presence of Zn(2+); a novel Ab was generated that specifically recognized this complex. By chelating Zn(2+), S100A12 significantly inhibited MMP-2, MMP-9, and MMP-3, and the Zn(2+)-induced S100A12 complex colocalized with these in foam cells in human atheroma. S100A12 may represent a new marker of this disease and may protect advanced atherosclerotic lesions from rupture by inhibiting excessive MMP-2 and MMP-9 activities by sequestering Zn(2+).

Arsenic exacerbates atherosclerotic lesion formation and inflammation in ApoE-/- mice

Exposure to arsenic-contaminated water has been shown to be associated with cardiovascular disease, especially atherosclerosis. We examined the effect of arsenic exposure on atherosclerotic lesion formation, lesion composition and nature in ApoE-/- mice. Early post-natal exposure (3-week-old mice exposed to 49 ppm arsenic as NaAsO(2) in drinking water for 7 weeks) increased the atherosclerotic lesion formation by 3- to 5-fold in the aortic valve and the aortic arch, without affecting plasma cholesterol. Exposure to arsenic for 13 weeks (3-week-old mice exposed to 1, 4.9 and 49 ppm arsenic as NaAsO(2) in drinking water) increased the lesion formation and macrophage accumulation in a dose-dependent manner. Temporal studies showed that continuous arsenic exposure significantly exacerbated the lesion formation throughout the aortic tree at 16 and 36 weeks of age. Withdrawal of arsenic for 12 weeks after an initial exposure for 21 weeks (to 3-week-old mice) significantly decreased lesion formation as compared with mice continuously exposed to arsenic. Similarly, adult exposure to 49 ppm arsenic for 24 weeks, starting at 12 weeks of age increased lesion formation by 2- to 3.6-fold in the aortic valve, the aortic arch and the abdominal aorta. Lesions of arsenic-exposed mice displayed a 1.8-fold increase in macrophage accumulation whereas smooth muscle cell and T-lymphocyte contents were not changed. Expression of pro-inflammatory chemokine MCP-1 and cytokine IL-6 and markers of oxidative stress, protein-HNE and protein-MDA adducts were markedly increased in lesions of arsenic-exposed mice. Plasma concentrations of MCP-1, IL-6 and MDA were also significantly elevated in arsenic-exposed mice. These data suggest that arsenic exposure increases oxidative stress, inflammation and atherosclerotic lesion formation.

Absence of p55 TNF receptor reduces atherosclerosis, but has no major effect on angiotensin II induced aneurysms in LDL receptor deficient mice

Background

The aim of the current study was to investigate the role of p55 TNF Receptor (p55 TNFR), the main signaling receptor for the pro-inflammatory cytokine tumor necrosis factor (TNF), in the development of two vascular disorders: atherosclerosis and angiotensin (Ang) II-induced abdominal aortic aneurysms (AAA).

Methodology/Principal Findings

p55 TNFR deficient mice were crossed to an LDL receptor deficient background and were induced for the development of either atherosclerosis or AngII-induced AAA, and compared to littermate controls, wild-type for p55 TNFR expression. p55 TNFR deficient mice developed 43% smaller atherosclerotic lesions in the aortic sinuses compared to controls. Moreover, expression of CD68, a macrophage specific marker, exhibited a 50% reduction in the aortic arches. Decreased atherosclerosis correlated with a strong down-regulation in the expression of adhesion molecules, such as VCAM-1 and ICAM-1, by p55 TNFR deficient endothelium. In addition, expression levels of the pro-inflammatory cytokines and chemokines TNF, IL-6, MCP-1 and RANTES were significantly reduced in aortas of p55 TNFR deficient mice. In contrast, in the AngII-induced model of AAA, p55 TNFR deficiency correlated with a slight trend towards increased aneurismal lethality, but the incidence of aortic rupture due to a dissecting aneurysm, and the expansion of the suprarenal aorta were not significantly different compared to controls.

Conclusion/Significance

We found that p55 TNFR expression promotes atherosclerosis, among other mechanisms, by enhancing expression of endothelial adhesion molecules, while it seems to have no major role in the development of AngII-induced AAA.

MIF deficiency reduces chronic inflammation in white adipose tissue and impairs the development of insulin resistance, glucose intolerance, and associated atherosclerotic disease

Chronic inflammation in white adipose tissue (WAT) is positively associated with obesity, insulin resistance (IR) and the development of type 2 diabetes. The proinflammatory cytokine MIF (macrophage migration inhibitory factor) is an essential, upstream component of the inflammatory cascade. This study examines whether MIF is required for the development of obesity, IR, glucose intolerance, and atherosclerosis in the LDL receptor-deficient (Ldlr(-/-)) mouse model of disease. Ldlr(-/-) mice develop IR and glucose intolerance within 15 weeks, whereas Mif(-/-)Ldlr(-/-) littermates are protected. MIF deficiency does not affect obesity and lipid risk factors but specifically reduces inflammation in WAT and liver, as reflected by lower plasma serum amyloid A and fibrinogen levels at baseline and under inflammatory conditions. Conversely, MIF stimulates the in vivo expression of human C-reactive protein, an inflammation marker and risk factor of IR and cardiovascular disease. In WAT, MIF deficiency reduces nuclear c-Jun levels and improves insulin sensitivity; MIF deficiency also reduces macrophage accumulation in WAT and blunts the expression of two proteins that regulate macrophage infiltration (intercellular adhesion molecule-1, CD44). Mechanistic parallels to WAT were observed in aorta, where the absence of MIF reduces monocyte adhesion, macrophage lesion content, and atherosclerotic lesion size. These data highlight the physiological importance of chronic inflammation in development of IR and atherosclerosis and suggest that MIF is a potential therapeutic target for reducing the inflammatory component of metabolic and cardiovascular disorders.