Interleukin-10 blocks atherosclerotic events in vitro and in vivo

Antiatherogenic effects of dietary plant sterols are associated with inhibition of proinflammatory cytokine production in Apo E-KO mice

Dietary phytosterols significantly reduce atherosclerosis in apo E-deficient mice. Because atherosclerosis is a chronic inflammatory disease, we investigated whether the antiatherogenic effects of phytosterols are associated with reductions in proinflammatory cytokine production as well as the effect of this diet on global immunocompetence. Apolipoprotein (apo) E-deficient mice were fed a cholesterol-supplemented diet in the presence or absence of 2% dietary phytosterols for 14 wk and then immunized with ovalbumin. The relations between plasma lipid concentrations, atherosclerotic lesions, and cytokine production and proinflammatory stimuli or foreign antigens were characterized. Phytosterol-enriched diets were strongly associated with reduced plasma cholesterol concentrations and atherosclerosis in conjunction with higher anti-inflammatory [interleukin (IL)-10] and lower proinflammatory cytokine [IL-6, tumor necrosis factor (TNF)-alpha] production. In contrast, development of cytokine and chemokine responses to ovalbumin was as strong as or even improved in the phytosterol-treated mice relative to controls. The antiatherogenic effects of dietary phytosterols in apo E-knockout mice were associated with beneficial alterations in both lipoprotein metabolism and inflammatory pathways. Decreased capacity to mount proinflammatory cytokine and chemokine responses to inflammatory stimuli did not interfere with the global immunocompetence of such mice. Thus, the desirable suppression of proinflammatory cytokine production that was associated with inhibition of atherogenesis did not impair the capacity to mount responses to foreign antigens.

Regulatory T cell responses: potential role in the control of atherosclerosis

PURPOSE OF REVIEW

Atherosclerosis is an inflammatory disease of the arterial wall where both innate and adaptive Th1-driven immunoinflammatory responses contribute to disease development. Th2-related responses have been shown to be either protective or pathogenic. Thus, it is unclear whether immunoregulatory activity can modulate disease development.

RECENT FINDINGS

Novel subtypes of T cells, called the regulatory T cells, have been shown recently to play a critical role in the maintenance of immunological tolerance against self and non-self antigens and prevent the development of various immunoinflammatory diseases. Preliminary studies suggest a potential role for this type of regulatory T cell response in atherosclerosis.

SUMMARY

Here we present a novel view of the immunoinflammatory response in atherosclerosis where natural and/or adaptive regulatory T cell responses modulate both Th1 and Th2 pathogenic responses and play a central role in counteracting disease initiation and progression.

Interleukin-18: Interleukin-10 ratio and in-hospital adverse events in patients with acute coronary syndrome

INTRODUCTION

Inflammatory mechanisms contribute to the development of acute coronary syndromes (ACS), and it has been suggested that an imbalance between pro- and anti-inflammatory responses may be an important determinant of recurrent cardiac events in this setting. Both increased serum levels of interleukin (IL)-18 and reduced concentrations of IL-10 have been shown to have prognostic significance in ACS. We sought to assess whether the ratio of serum IL-18/IL-10 levels has higher positive predictive value than the individual measurement of IL-10 and IL-18 in patients admitted to hospital with ACS.

METHODS

We recruited 107 consecutive patients (79 men, mean age 65+/-12 years) with ACS (41 STEMI, 39 NSTEMI and 27 UA). The composite of cardiac death, recurrence of unstable angina, re-infarction, life threatening arrhythmias, and urgent revascularization during hospitalization was the pre-specified study end-point. We assessed independent predictors of the combined end-point using multiple logistic regression analysis. Serum IL-10 and IL-18 levels were measured at study entry using commercially available ELISAs.

RESULTS

During hospitalization 44 patients (41%) had events and 63 (59%) had no events. Significantly higher odd ratios were found for IL-18/IL-10 ratio (1.74 95% CI 1.09-2.78) compared to individual IL-18 (1.46 95% CI 0.93-2.27) and 1/IL-10 (1.63 95% CI 1.04-2.56) measurements.

CONCLUSION

Serum IL-18/IL-10 ratio is an independent predictor of in-hospital adverse events in patients with ACS. Our study strongly endorses the notion that an imbalance between pro and anti-inflammatory forces predisposes to plaque disruption and recurrent cardiovascular events.

Can worms defend our hearts? Chronic helminthic infections may attenuate the development of cardiovascular diseases

The established risk factors for atherosclerosis fail to fully explain the extent and severity of coronary artery diseases in 50% of the patients. Thus, the causative agents and processes, which may be involved in the pathogenesis of atherosclerosis, are being sought. Notoriously, atherosclerosis and cardiovascular event rates are much lower in developing countries. Clinically, severe infections by intracellular pathogens are widespread mostly in developing countries with poor sanitation, nutrition and massive worm infections. A link between atherosclerosis and helminth infections has never been examined. Based on the present knowledge of immune and infectious mechanisms related to atherosclerosis, it is proposed that chronic helminthic infections can have a significant bearing on the epidemiology of cardiovascular diseases. How can helminthic infections affect the cardiovascular risk? (1) Helminths evade or suppress host immune responses, by producing anti-inflammatory and other immunomodulatory molecules. (2) Helminths induce chronic Th2 activation, which can modify cytokine profiles and immunological responses to heat shock proteins, Chlamydia pneumoniae and cytomegalovirus. (3) The chronic Th2 profile may modulate monocyte activation and chemotaxis to inflammatory sites (atherosclerotic plaques). (4) Chronic Th2 activation may lead to a cytokine profile that could be beneficial for attenuation of atherosclerosis development (upregulation of IL-4, IL-10 and IL-13 and downregulation of proinflammatory cytokines). (5) Helminthic infections may reduce plasma LDL level not only by affecting the host nutrition, but also via modulation of naturally occurring antibodies to cholesterol. Studies are needed to clarify these suggestions. If the hypothesis that helminthic infections impact atherosclerosis is correct, it should be taken into consideration in atherosclerosis immunomodulation therapy and especially in the design of vaccines and vaccine trials.

SLE, atherosclerosis and cardiovascular disease

Atherosclerosis is an inflammatory disease and the major cause of cardiovascular disease (CVD) in general. Atherosclerotic plaques are characterized by the presence of activated immune competent cells, but antigens and underlying mechanisms causing this immune activation are not well defined. During recent years and with improved treatment of acute disease manifestations, it has become clear that the risk of CVD is very high in a prototypic autoimmune disease, systemic lupus erythematosus (SLE). SLE-related CVD and atherosclerosis are important clinical problems but may in addition also shed light on how immune reactions are related to premature atherosclerosis and atherothrombosis. A combination of traditional and nontraditional risk factors, including dyslipidaemia (and to a varying degree hypertension, diabetes and smoking), inflammation, antiphospholipid antibodies (aPL) and lipid oxidation are related to CVD in SLE. Premature atherosclerosis in some form leading to atherothrombosis is likely to be a major underlying mechanism, though distinctive features if any, of SLE-related atherosclerosis when compared with 'normal' atherosclerosis are not clear. One interesting possibility is that factors such as inflammation or aPL make atherosclerotic lesions in autoimmune disease more prone to rupture than in 'normal' atherosclerosis. Whether premature atherosclerosis is a general feature of SLE or only affects a subgroup of patients remains to be demonstrated. Treatment of SLE patients should also include a close monitoring of traditional risk factors for CVD. In addition, attention should also be paid to nontraditional risk factors such as inflammation and SLE-related factors such as aPL. Hopefully novel therapeutic principles will be developed that target the causes of the inflammation and immune reactions present in atherosclerotic lesions.

Induction of coronary arteritis with administration of CAWS (Candida albicans water-soluble fraction) depending on mouse strains

The intraperitoneal administration of CAWS (water-soluble extracellular polysaccharide fraction obtained from the culture supernatant of Candida albicans) to mice induces coronaritis similar to Kawasaki disease. We analyzed differences in the production of cytokines involved in the occurrence of coronary arteritis among mouse strains, C3H/HeN, C57BL/6, DBA/2 and CBA/J that were injected with CAWS at 4 mg/mouse for 5 consecutive days in the first week and the fifth week of administration. The incidence of arteritis was 100% in C57BL/6, C3H/HeN and DBA/2 mice, but only 10% in CBA/J mice. The coronary arteritis observed in DBA/2 mice was the most serious, with several mice expiring during the observation period. The CAWS-sensitive strains revealed increased levels of IL-6 and IFN-gamma during the course of a specific response to CAWS by spleen cells. In contrast, IL-10 levels were observed to increase markedly in CAWS-resistant CBA/J mice, but not the CAWS-sensitive strains. However, TNF-alpha levels were more elevated only in DBA/2 mice. The difference in disease development and cytokine production strongly suggests that the genetic background of the immune response to CAWS contributes to the occurrence of coronary arteritis.

Interleukin 10 attenuates neointimal proliferation and inflammation in aortic allografts by a heme oxygenase-dependent pathway

Interleukin 10 (IL-10) is a pleiotropic cytokine with well known antiinflammatory, immunosuppressive, and immunostimulatory properties. Chronic allograft rejection, characterized by vascular neointimal proliferation, is a major cause of organ transplant loss, particularly in heart and kidney transplant recipients. In a Dark Agouti to Lewis rat model of aortic transplantation, we evaluated the effects of a single intramuscular injection of a recombinant adeno-associated viral vector (serotype 1) encoding IL-10 (rAAV1-IL-10) on neointimal proliferation and inflammation. rAAV1-IL-10 treatment resulted in a significant reduction of neointimal proliferation and graft infiltration with macrophages and T and B lymphocytes. The mechanism underlying the protective effects of IL-10 in aortic allografts involved heme oxygenase 1 (HO-1) because inhibition of HO activity reversed not only neointimal proliferation but also inflammatory cell infiltration. Our results indicate that IL-10 attenuates neointimal proliferation and inflammatory infiltration and strongly imply that HO-1 is an important intermediary through which IL-10 regulates the inflammatory responses associated with chronic vascular rejection.

Immunomodulation to combat atherosclerosis: the potential role of immune regulatory cells

Atherosclerosis is an inflammatory disease of the arterial wall that carries an important socio-economic burden. The available data strongly suggest that both innate and adaptive immuno-inflammatory mechanisms are the major determinants of plaque complications (called instability). Therefore, most of the important advances in the comprehension of the mechanisms of atherosclerosis came from studies that aimed at the elucidation of the critical components involved in the modulation of the immuno-inflammatory response in experimental models of atherosclerosis. As the T helper (Th)1-driven immune response has been consistently shown to promote atherosclerosis, the general belief is that immunomodulation through Th2 may be suitable to halt the disease process. Here, a novel view of the immuno-inflammatory response in atherosclerosis is presented, in which the natural and/or adaptive regulatory responses modulate both Th1 and Th2 responses, and play a central role in counteracting disease initiation and progression.

Upregulation of TNF-alpha-induced ICAM-1 surface expression by adenylate cyclase-dependent pathway in human endothelial cells

The level of adhesion molecules expressed at the endothelial cell surface is critical in the control of inflammation. Adenylate cyclase (AC) activity allowing cyclic adenosine monophosphate (cAMP) production can modulate the inflammatory process. We investigated the AC-dependent modulation of ICAM-1 surface expression in human umbilical venous endothelial cells (HUVEC). Pretreatment of HUVEC with forskolin significantly upregulated tumor necrosis factor alpha (TNF-alpha)- and interleukin-1 alpha (IL1-alpha)-induced ICAM-1 surface expression exclusively after a prolonged time of incubation with forskolin (at least 7-8 h). A poorly metabolizable analog of cAMP, dibutyryl-cAMP, mimicked forskolin effect on ICAM-1 surface expression. Protein kinase A (PKA) inhibitor H89 prevented forskolin effect on ICAM-1 surface expression. Upregulation of ICAM-1 surface level occurred through the increase in its mRNA levels and also to a subsequent activation of ICAM-1 intracellular trafficking towards cell surface. Stimulation by agonists of beta-adrenergic receptors did not alter the TNF-alpha-induced ICAM-1 surface expression. Pretreatment of HUVEC with pertussis toxin, which is known to activate AC through Gialpha inhibition, upregulated mRNA levels and surface expression of ICAM-1 induced by TNF-alpha. This effect was serum-dependent, since ICAM-1 expression was no more upregulated by pertussis toxin in cells cultured in 1% instead of 20% serum-enriched medium. However, forskolin treatment of HUVEC did not modify their overall adhesive properties. In conclusion, a persistent cAMP level elevation activating PKA is able to enhance ICAM-1 expression at the cell surface of endothelial cells placed under pro-inflammatory conditions. Combination of activation of gene transcription and membrane targeting may account for this augmentation.

Adeno-associated virus vector-mediated interleukin-10 gene transfer inhibits atherosclerosis in apolipoprotein E-deficient mice

Inflammation is a major contributor to atherosclerosis by its effects on arterial wall biology and lipoprotein metabolism. Interleukin-10 (IL-10) is an anti-inflammatory cytokine that may modulate the atherosclerotic disease process. We investigated the effects of adeno-associated virus (AAV) vector-mediated gene transfer of IL-10 on atherogenesis in apolipoprotein E (ApoE)-deficient mice. A murine myoblast cell line, C2C12, transduced with AAV encoding murine IL-10 (AAV2-mIL10) secreted substantial amounts of IL-10 into conditioned medium. The production of monocyte chemoattractant protein-1 (MCP-1) by the murine macrophage cell line, J774, was significantly inhibited by conditioned medium from AAV2-mIL10-transduced C2C12 cells. ApoE-deficient mice were injected with AAV5-mIL10 into their anterior tibial muscle at 8 weeks of age. The expression of MCP-1 in the vascular wall of the ascending aorta and serum MCP-1 concentration were decreased in AAV5-mIL10-transduced mice compared with AAV5-LacZ-transduced mice. Oil red-O staining of the ascending aorta revealed that IL-10 gene transfer resulted in a 31% reduction in plaque surface area. Serum cholesterol concentrations were also significantly reduced in AAV5-mIL10-transduced mice. To understand the cholesterol-lowering mechanism of IL-10, we measured the cellular cholesterol level in HepG2 cells, resulting in its significant decrease by the addition of IL-10 in a dose-dependent manner. Furthermore, IL-10 suppressed HMG-CoA reductase expression in the HepG2 cells. These observations suggest that intramuscular injection of AAV5-mIL10 into ApoE-deficient mice inhibits atherogenesis through anti-inflammatory and cholesterol-lowering effects.

Circulating levels of proinflammatory cytokines and neutrophil-platelet aggregates in patients with coronary artery disease

Several lines of evidence indicate that increased inflammatory activity in peripheral blood is associated with the acute coronary syndrome. Systemic inflammation in clinically stable conditions of coronary artery disease has been less studied. We examined cytokine profiles in 20 patients who had acute coronary syndrome, 45 who had angiographically verified coronary artery disease and stable angina pectoris, and 45 healthy controls. Circulating levels of C-reactive protein, interleukin-1 receptor antagonist, interleukin-2 receptor, interleukin-6, interleukin-10, and interleukin-18 were determined. Subpopulations of peripheral immune cells, including neutrophil-platelet aggregates, were analyzed by 3-color flow cytometry using a panel of monoclonal antibodies. Patients who had acute coronary syndrome and stable angina pectoris had significantly higher levels of C-reactive protein, interleukin-6, and interleukin-1 receptor antagonist than did controls, whereas levels of interleukin-2 receptor, interleukin-10, and interleukin-18 were similar across groups. Patients had significantly more neutrophils, and the numbers of neutrophil-platelet aggregates were particularly large in patients who had stable angina pectoris. High levels of C-reactive protein, interleukin-6, and interleukin-1 receptor antagonist in patients were significantly related to numbers of neutrophils and neutrophil-platelet aggregates but not to other immune cell subpopulations. The data suggest that the interaction between neutrophils and platelets is an important component of proinflammatory activity seen in peripheral blood of stable and unstable forms of coronary artery disease.

Interleukin-10 enhances the oxidized LDL-induced foam cell formation of macrophages by antiapoptotic mechanisms

Interleukin (IL)-10 may have a therapeutic potential in atherosclerosis, but its mechanisms of action have not been clarified. Foam cell formation is a key event in atherogenesis, and apoptosis of these lipid-laden cells may promote plaque destabilization. We sought to explore whether IL-10 could have plaque-stabilizing properties in acute coronary syndromes (ACS). We studied the effect of IL-10 on oxidized low density lipoprotein (oxLDL)-stimulated THP-1 cells and monocyte-derived macrophages from ACS patients and healthy controls using different experimental approaches. Our main findings were: i) IL-10 enhances lipid accumulation in oxLDL-stimulated THP-1 macrophages, at least partly by counteracting oxLDL-induced apoptosis; ii) This antiapoptotic effect of IL-10 involves increased expression of the antiapoptotic genes Bfl-1 and Mcl-1, accompanied by protective effects on mitochondria function; iii) By silencing Bfl-1 and Mcl-1 genes using siRNAs, we were able to abolish this IL-10-mediated effect on lipid accumulation; iv) IL-10 also induced lipid accumulation in oxLDL-stimulated macrophages from patients with ACS, but not in macrophages from healthy controls; v) In ACS patients, this enhancing effect of IL-10 on lipid accumulation was accompanied by enhanced Mcl-1 expression. No such antiapoptotic effect was seen in macrophages from healthy controls. These findings suggest a new mechanism for the effect of IL-10 in atherosclerosis, possibly contributing to plaque stabilization.

The pathogenesis of atherosclerosis

Worldwide, more people die of the complications of atherosclerosis than of any other cause. It is not surprising, therefore, that enormous resources have been devoted to studying the pathogenesis of this condition. This article attempts to summarize present knowledge on the events that take place within the arterial wall during atherogenesis. Classical risk factors are not dealt with as they are the subjects of other parts of this book. First, we deal with the role of endothelial dysfunction and infection in initiating the atherosclerotic lesion. Then we describe the development of the lesion itself, with particular emphasis on the cell types involved and the interactions between them. The next section of the chapter deals with the events leading to thrombotic occlusion of the atherosclerotic vessel, the cause of heart attack and stroke. Finally, we describe the advantages--and limitations--of current animal models as they contribute to our understanding of atherosclerosis and its complications.

Gene therapy of atherosclerosis

Atherosclerosis and related diseases are the leading cause of death in Western world. The disease process begins with the formation of fatty streaks already during the first decade of life but does not manifest clinically until several decades later. Gene therapy is a potential new way to target multiple factors playing a role in the development and progression of atherosclerosis. A great number of genes involved in the development of atherosclerosis have been identified and have been tested both in vitro and in vivo as potential new targets for therapy. Pre-clinical experiments have shown the feasibility and safety of several gene therapy applications for the treatment of atherosclerosis and clinical trials have also provided evidence for the applicability of gene therapy for the treatment of cardiovascular diseases. In this review we discuss vectors and potential gene therapy approaches for intervention and therapy of atherosclerosis.

Enhancing anti-inflammatory cytokine IL-10 may be beneficial for acute coronary syndrome

Inflammation is one of the basic biological responses against vascular injury. It has been demonstrated, however, that inflammation is an important pathogenic feature in atherosclerotic lesions. Previous data showed that pro-inflammatory cytokines played an important role in acute coronary events. A complex intravascular inflammatory response is also an integral component of atherosclerotic plaque dynamic instability, and the imbalance between anti-inflammatory mechanisms and pro-inflammatory factors, in favor of the pro-inflammatory factors, will result in rupture of atherosclerotic plaque. Interluekine-10 (IL-10), which is produced by various inflammatory cells, especially macrophages, has multifaceted anti-inflammatory properties, including inhibition of the prototypic pro-inflammatory transcription factor nuclear factor-kappaB, leading to suppressed cytokine production, inhibition of matrix degrading metalloproteinase production, reduction of tissue factor expression, inhibition of apoptosis of macrophages and monocytes after infection, and promotion of the phenotypic switch of lymphocytes into the Th2 phenotype. All these inflammatory mechanisms have been shown to play a pivotal role for atheroslerotic lesion development and progression, indicating a potential regulatory role of IL-10. More recent data showed that decreased plasma concentration of anti-inflammatory cytokine IL-10 was associated with acute coronary syndrome. Therefore, we hypotheses that enhancing anti-inflammatory cytokine IL-10 may be a promising approach for the therapy of acute coronary diseases.

Circulating monocytes in patients with acute coronary syndromes lack sufficient interleukin-10 production after lipopolysaccharide stimulation

Acute coronary syndromes (ACS) are associated with inflammation resulting from monocyte activation. We sought for differences in the production of pro- and anti-inflammatory cytokines by monocytes from patients with ACS. C-reactive protein (CRP) and neopterin were measured in 22 patients with acute coronary syndromes, 50 patients with stable vascular disease and 22 healthy controls. Production of tumour necrosis factor (TNF)-alpha and interleukin (IL)-10 was determined after, respectively, 6 and 24 h of incubation of full blood with lipopolysaccharide (LPS). Levels of CRP [median, interquartile range (IQR)][1.5 mg/l (0.8-4.5) ACS patient versus 2.1 (0.9-3.6) stable disease versus 0.4 (0.3-1.2) healthy controls] (P < 0.001) and neopterin [7.4 nmol/l (6.0-8.7) ACS patient versus 7.1(6.0-8.9) stable disease versus 6.4 (5.6-7.3) healthy controls] (P = 0.07) were higher in both the patient groups. IL-10 production after LPS stimulation was greatly reduced in patients with acute coronary syndromes (16 175 pg/ml, 7559-28 470 pg/ml) as opposed to patients with stable disease (28 379 pg/ml, 12 601-73 968 pg/ml) and healthy controls (63 830 pg/ml, 22 040-168 000 pg/ml) (P = 0.003). TNF-alpha production was not signi fi cantly different between the groups [7313 pg/ml (4740-12 615) ACS patient versus 11 002 (5913-14 190) stable disease versus 8229 (5225-11 364) healthy controls] (P = 0.24). Circulating monocytes in unstable coronary syndromes produce equal amounts of TNF-alpha but less IL-10 after stimulation with LPS in vitro as compared with healthy controls. We hypothesize that, in acute coronary syndromes, the production proinflammatory cytokines is not counterbalanced by anti-inflammatory cytokines such as IL-10.

Atherosclerosis and the immune system

The immune system is involved at all stages of the atherosclerotic disease process. Innate immunity, represented by macrophages and other cells, is directly activated by microbial components and possibly also by autologous lipids and proteins. It elicits inflammatory activity, which is a key component of the atherosclerotic lesion. Adaptive immunity is initiated by recognition of disease-related antigens, which include oxidatively modified lipoproteins, heat shock proteins and microbial macromolecules. In the artery wall, adaptive immune recognition mainly leads to Thl effector responses, which are characterized by secretion of proinflammatory cytokines and by activation of macrophages and vascular cells. Therefore, both the innate and adaptive arms of the immune system lead to inflammation in the developing atherosclerotic lesion. Interestingly, several effector pathways of cellular as well as humoral immunity tend to counteract proatherogenic, proinflammatory immunity. The notion that immunity plays an important role in the development of atherosclerosis has focused attention on a number of potential novel targets for intervention based on modulation of such immune responses.

The A-1087IL-10 allele is associated with cardiovascular disease in SLE

The risk of cardiovascular disease (CVD) in SLE patients is very high. It is therefore surprising that IL-10 has been discussed both as pathogenic in SLE and as an atheroprotective cytokine. In contrast, TNF is believed to be atherogenic and we recently reported that raised activity in the TNF-system is implicated in SLE-related CVD. Twenty-six (aged 52 +/- 8 years) female patients with SLE and a history of CVD (myocardial infarction, angina, stroke or claudication) were compared with 26 age-matched SLE patients without CVD (SLE controls) or 26 age-matched population controls. The -1087IL-10 gene polymorphism was determined by PCR with restriction endonuclease mapping. Serum IL-10 and TNF-levels were determined by ELISA. The A allele frequency of -1087IL-10 gene in SLE/CVD was higher than in SLE controls (0.62 versus 0.42, p < 0.05). Ten (38%) of 26 SLE/CVD exhibited IL-10 AA genotype compared with five (19%) of 26 SLE controls. Serum IL-10 and TNF-levels were raised in SLE/CVD compared with SLE controls or population controls (p < 0.001). Furthermore, in SLE/CVD, a significantly reduced IL-10:TNF ratio was observed in patients with IL-10 AA genotype compared with AG or GG genotype (0.56 versus 0.77 versus 1.24, p < 0.05). In SLE controls and population controls, individuals with IL-10 GG genotype tended to have higher IL-10:TNF ratio. In conclusion, the A-1087IL-10 allele which has been reported to cause a lower capacity for IL-10 production could contribute to CVD in SLE. Furthermore, the IL-10 AA genotype is associated with reduced ratio of atheroprotective to atherogenic cytokines in SLE patients with CVD.

Interleukin-10 attenuates the response to vascular injury

BACKGROUND

The inflammatory response to vascular injury is characterized by expression of cytokines, growth factors, and chemokines that conspire to promote vessel remodeling and intimal hyperplasia (IH). Interleukin-10 (IL-10) is a multifunctional cytokine that has several anti-inflammatory properties in vitro. Few studies have evaluated the effects of IL-10 in experimental atherosclerosis. The purpose of the present study was to determine the influence of IL-10 on vascular inflammation and IH following mechanical injury.

METHODS

Wire carotid injury was performed in wild-type (WT) mice with and without IL-10 treatment. Immunohistochemistry, PCR, and ELISA assays were used to examine vessel production of basic fibroblast growth factor (bFGF), monocyte chemotactic protein-1 (MCP-1), and nuclear factor kappa B (NFkappaB). Vessels were morphometrically analyzed for IH.

RESULTS

Carotid injury induced early expression of MCP-1 and bFGF that was abrogated in mice treated with IL-10. Similarly, injury-induced expression of NFkappaB message and protein was attenuated in mice receiving exogenous IL-10. Compared to untreated mice, IL-10 markedly decreased levels of IH. Interestingly, carotid injury in IL-10-deficient mice resulted in an augmented IH response compared to injured WT mice.

CONCLUSIONS

In an in vivo model of direct vascular injury, IL-10 decreased expression of the pro-inflammatory transcription factor, NFkappaB, and the mitogenic chemokine and growth factor, MCP-1 and bFGF, respectively. These observations were associated with IL-10-induced attenuation of IH. Furthermore, endogenous IL-10 appeared to suppress the injury response. In conclusion, exogenously delivered IL-10 may represent a clinically relevant anti-inflammatory strategy for post-injury intimal hyperplasia.

IL-5 links adaptive and natural immunity in reducing atherosclerotic disease

Oxidized LDL induces changes in several facets of the immune system, although the relationships between these facets and their contributions to atherogenesis have yet to be fully elucidated. A report in this issue of the JCI provides a novel demonstration of the adaptive immune system influencing the production of natural antibodies. The results demonstrate that injection of malondialdehyde-modified LDL promotes a Th2 response that in turn increases the titers of the natural antibody T15/EO6, which recognizes the oxidized phospholipid POVPC. Atherosclerotic lesion size in LDL receptor-deficient mice is reduced as a consequence of the increase in natural antibody titers, and IL-5 is identified as the link between the adaptive and natural immune systems.

Impact of IL-1β on flow-induced outward arterial remodeling

BACKGROUND

Flow reduction upregulates arterial wall interleukin 1beta (IL-1beta), and IL-1beta independently modulates intimal hyperplasia under low flow conditions. We hypothesized that IL-1beta expression is also augmented under high flow, and outward remodeling occurs by way of IL-1beta-dependent mechanisms.

METHODS

Carotid artery (CA) flow was surgically augmented in rabbits (n = 20). CAs were harvested at 1, 3, 7, and 14 days, and assayed via quantitative reverse transcriptase-polymerase chain reaction. IL-1 receptor I null mice (KO) and wild-type controls underwent unilateral CA ligation and harvest 4 weeks later to assess the impact of increased flow on the contralateral CA (n = 82).

RESULTS

The rabbit model led to an immediate 36% increase in contralateral flow (P = .01) with an 80% increase at 14 days (P = .016) with subsequent positive remodeling. High flow induced IL-1beta messenger RNA expression (114-fold at 1 day, P < .05), with levels remaining elevated through 14 days (61-fold, P < .05). In murine experiments, CA ligation resulted in a 44% increase in contralateral flow. Wild-type and KO animals responded with equivalent 83% and 78% increases in luminal area (P = .87).

CONCLUSIONS

Positive and negative perturbations of arterial blood flow induce IL-1beta in a time-dependent fashion. However, as opposed to intimal hyperplasia after flow reduction, positive arterial remodeling in response to increased flow occurs via IL-1beta independent mechanisms.

Interleukin-10 serum levels and systemic endothelial vasoreactivity in patients with coronary artery disease

OBJECTIVES

Because the endothelium is a major target for inflammatory cytokines, we investigated whether elevated interleukin (IL)-10 serum levels are associated with improved endothelial vasoreactivity in patients with coronary artery disease (CAD).

BACKGROUND

Chronic inflammation plays a pivotal role in the progression of atherosclerosis. Interleukin-10 is an anti-inflammatory cytokine that exerts important protective effects on atherosclerotic lesion development in experimental animals.

METHODS

Vasoreactivity was assessed in 65 male patients with documented CAD by measuring endothelium-dependent (acetylcholine [ACh] 10 to 50 microg/min) and endothelium-independent (sodium nitroprusside [SNP] 2 to 8 microg/min) forearm blood flow (FBF) responses using venous occlusion plethysmography.

RESULTS

Serum levels of IL-10 were significantly correlated with ACh-induced FBF responses (r = 0.31, p < 0.02), but not with SNP responses. Importantly, if IL-10 serum levels were increased in patients with elevated C-reactive protein (CRP) levels, no impairment of ACh-stimulated FBF response was observed. On multivariate analysis, including low-density lipoprotein cholesterol, smoking, hypertension, diabetes, clinical status of the patients, and statin and/or angiotensin-converting enzyme inhibitor treatment, only IL-10 (p < 0.02) and CRP serum levels (p < 0.02) were significant independent predictors of ACh-induced FBF responses.

CONCLUSIONS

Thus, increased IL-10 serum levels are associated with improved systemic endothelial vasoreactivity in patients with elevated CRP serum levels, demonstrating that the balance between pro- and anti-inflammatory mediators is a major determinant of endothelial function in patients with CAD.

Comparative effects of AT1-antagonism and angiotensin-converting enzyme inhibition on markers of inflammation and platelet aggregation in patients with coronary artery disease

OBJECTIVES

We evaluated whether renin-angiotensin system (RAS) blockade attenuates cardiovascular events.

BACKGROUND

Because inflammation and enhanced thrombogenesis are hallmarks of atherosclerosis, we assessed whether RAS inhibition elicits anti-inflammatory and anti-aggregatory effects.

METHODS

Interleukin 6 (IL-6), high-sensitivity C-reactive protein (hsCRP), metalloprotease 9 (MMP-9), and interleukin 10 (IL-10) were determined in patients with coronary artery disease (CAD) and arterial hypertension six to eight weeks after coronary angioplasty (low-density lipoprotein serum levels <150 mg/dl). Patients were randomized double-blind to either 20 mg enalapril (ENAL, n = 27) or 300 mg irbesartan (IRB, n = 21) for 3 months. Blood samples were drawn at baseline and at three months. Thromboxane A2-induced platelet aggregation was determined turbidimetrically; urine bicyclo-prostaglandin E2 (PGE(2)) and inflammatory markers were measured by enzyme-linked immunosorbent assay technique.

RESULTS

Both treatment regimens enhanced serum IL-10 levels (IRB p < 0.001, ENAL p < 0.03) and reduced serum MMP-9 protein (IRB p < 0.001, ENAL p < 0.05) and MMP-9 activity (IRB p < 0.005, ENAL p < 0.05). Only IRB reduced serum IL-6 and hsCRP levels significantly compared with baseline (p < 0.01), whereas ENAL did not (hsCRP p < 0.02 IRB vs. ENAL, p < 0.01 IRB vs. ENAL). Platelet aggregation was only reduced by IRB (p < 0.001, ENAL p < 0.06, IRB vs. ENAL p < 0.001) while urine PGE(2) levels remained unchanged.

CONCLUSIONS

Angiotensin-converting enzyme (ACE) inhibition and angiotensin II type 1 receptor (AT1) blockade reduced serum MMP-9 protein/activity to a similar extent, and only AT1 blockade reduced hsCRP, IL-6, and platelet aggregation in patients with CAD. Thus, AT1-blockade appears to exert stronger systemic anti-inflammatory and anti-aggregatory effects compared with ACE inhibition.

Intramuscular gene transfer of interleukin-10 cDNA reduces atherosclerosis in apolipoprotein E-knockout mice

Atherosclerosis has a close relationship to inflammation, particularly T helper type 1 lymphocyte (Th1) response. Interleukin-10 (IL-10), is thought to suppress Th1 response. To target therapeutic strategy for atherosclerosis, we tested whether IL-10 gene transfer suppresses atherosclerosis in apolipoprotein E-knockout (apoE-KO) mice. Four-week-old apoE-KO mice were divided into two groups and either murine IL-10 cDNA plasmid or empty control vector was transferred to the femoral muscle with the use of Hemagglutinating virus of Japan (HVJ)-liposome. At 1 week after transfection, high cholesterol diet was started and continued for 8 weeks. After euthanasia, histological studies of atherosclerotic lesions and quantitative RT-PCR for Th1 cytokines (IL-12 and IFN-gamma) in spleens were performed. IL-10 cDNA gene transfer to the muscle increased plasma IL-10 levels and depressed expression of Th1 cytokines without changing plasma cholesterol levels. IL-10 gene transfer significantly reduced the atherosclerotic plaque area and the macrophage infiltrated area. IL-12 and IFN-gamma mRNA expressions in spleens and plasma IFN-gamma levels were decreased by IL-10 gene transfer. Therefore, IL-10 gene transfer changed the Th1 response and suppressed atherosclerotic lesion formation in apoE-KO mice. IL-10 could be a new target as a therapeutic tool for the treatment of atherosclerosis.

Renovascular disease is associated with low producer genotypes of the anti-inflammatory cytokine interleukin-10

Cytokines are important mediators of inflammatory and proliferative responses in disease states including atherosclerosis. Genetic variations in cytokine production could potentially influence the outcome of these responses. The aim of this study was to determine whether cytokine gene polymorphism might influence the development of atherosclerotic renal artery stenosis. Sixty-six patients with atherosclerotic renal artery stenosis and 100 normal healthy individuals were genotyped for interleukin-10 (IL-10), tumor necrosis factor-alpha (TNF-alpha), IL-6, and IL-2 promoter region polymorphism. TNF-a, TNF-d, and IL-10 microsatellite polymorphisms were also analyzed. The frequency of the anti-inflammatory cytokine IL-10 promoter (-1082 A positive) GA and AA genotypes which are associated with low production were higher in the patient group when compared to the control group. The AA-TT-AA homozygous genotype combination of three single-nucleotide polymorphisms at -1082, -819, and -592 in the IL-10 gene was also observed at a higher frequency in the patient group compared to the controls. The frequency of TNF-alpha, IL-6, and IL-2 polymorphisms did not show any significant difference between the patient and control groups. To correlate IL-10 genotypes with differences in IL-10 protein expression, in vitro mRNA and protein levels were analyzed in lipopolysaccharide-stimulated peripheral blood mononuclear cells from 22 patients with renal artery stenosis and 33 controls. Individuals genotyped as A positive at position -1082 produced lower levels of IL-10 protein and had lower copy numbers of mRNA when compared to individuals genotyped as A negative in both patient and control groups. The increased frequency of the low producer IL-10 promoter, -1082 A-positive genotype in patients with renal artery stenosis, suggests that IL-10 may protect against the development of atherosclerotic renovascular disease.

Anti-inflammatory cytokine profile in acute coronary syndromes: behavior of interleukin-10 in association with serum metalloproteinases and proinflammatory cytokines

BACKGROUND

The anti-inflammatory cytokine interleukin-10 (IL-10) downregulates the production of metalloproteinases (MMPs) and upregulates the production of their tissue inhibitors (TIMPs). The aim of this study was to assess the levels of IL-10 in patients with acute myocardial infarction (AMI) and unstable angina (UA), as well as to investigate the relationship of circulating IL-10 with the levels of MMPs (MMP-1, -2, -9), their tissue inhibitor (TIMP-1), pro-inflammatory cytokines (IL-6, tumor necrosis factor (TNF)-alpha) and serum lipids in the same patient population.

METHODS

Serum MMP-1, -2, -9, TIMP-1, IL-6, TNF-alpha and IL-10 were measured by ELISA assays in 23 patients with AMI and 20 patients with UA after their hospital admission, as well as in 16 healthy controls subjects. The lipid profile was assessed by measuring the serum levels of total cholesterol, HDL-cholesterol, LDL-cholesterol and triglycerides.

RESULTS

AMI patients exhibited significantly higher serum levels of IL-10 as compared with those of UA patients and healthy controls (both P=0.005). In contrast, there was no significant difference in IL-10 levels between UA patients and healthy controls. In AMI patients there was a statistically significant positive correlation of serum IL-10 with the levels of MMP-9 (rho=0.588, P=0.003), IL-6 (rho=0.502, P=0.015) and HDL-cholesterol (rho=0.697, P<0.001), as well as a significant negative correlation with the levels of triglycerides (rho=-0.417, P=0.048).

CONCLUSIONS

Our results suggest that UA is associated with low serum activity of IL-10, while a significant elevation of this anti-inflammatory cytokine accompanies the peripheral immune responses of AMI. This observation indicates that different patterns of inflammatory reactions are implicated in the pathophysiology of two clinical conditions.

IL-10 inhibits vascular smooth muscle cell activation in vitro and in vivo

The anti-inflammatory cytokine IL-10 inhibits intimal hyperplasia after stent implantation via a powerful inactivation of monocytes. We tested the hypothesis that IL-10 may also inhibit vascular smooth muscle cell (SMC) activation via the inhibition of the NF-kappaB/I-kappaB system. The IL-10 receptor was detected in rat SMCs in vitro and in vivo. In LPS-stimulated rat SMCs, 1 ng/ml recombinant murine IL-10 (mIL-10) reduced I-kappaBalpha and I-kappaBbeta degradation, NF-kappaB activation, as well as the expression of the NF-kappaB-dependent gene IL-6 by 32%, 31%, 75%, and 19%, respectively (P < 0.05 for all). Similar results were obtained in vivo 6 h and 4 days after balloon abrasion of the rat aorta, a model in which intimal hyperplasia results essentially from SMC activation. Moreover, mIL-10 reduced SMC proliferation and migration in vitro (by 60% for both, P < 0.0001), resulting in reduced SMC proliferation and intimal growth 14 days after balloon abrasion of the rat aorta (by 76% and 75%, respectively; P < 0.005). In conclusion, mIL-10 has a direct inhibitory effect on SMCs in vitro and in vivo. This effect is mediated in part by NF-kappaB inactivation and may participate in the overall protective effect of IL-10 on postangioplasty restenosis.

Severe Hypercholesterolaemia Leads to Strong Th2 Responses to an Exogenous Antigen

Severe hypercholesterolaemia is associated with decreased levels of immunoglobulin G2a (IgG2a) antibodies [T-helper 1 (Th1) response] to modified malondialdehyde-modified low-density lipoprotein (MDA-LDL) and increased levels of Th2-dependent IgG1 antibodies in apolipoprotein E-deficient (apoE(-/-)) mice. To investigate whether this reflects a general pattern of metabolic regulation of the humoral immune response, apoE(-/-) mice were fed diets resulting in different degrees of hypercholesterolaemia and immunized with keyhole limpet haemocyanin (KLH) in aluminium hydroxide. Cholesterol levels for different treatment groups ranged from 14 to 77 mmol/l in serum and from 10 to 39 mmol/g in liver. Mice with severe hypercholesterolaemia had increased IgG1 antibodies to MDA-LDL and decreased IgG2a anti-MDA-LDL. Importantly, titres of IgG2a antibodies to KLH were also decreased, while IgE anti-KLH was increased, with a corresponding induction of interleukin-4 (IL-4) and IL-10 and a decrease in interferon-gamma (IFN-gamma) in KLH-stimulated spleen cells in vitro. Thus, hypercholesterolaemia clearly affects antibody production both to the autoantigen MDA-LDL and to the exogenous antigen KLH, favouring antibody isotypes (IgG1 and IgE) that are dependent on Th2 help to B cells. Nuclear receptors ligated by oxidized lipid derivatives modulate T-cell responses, and it is speculated that this mechanism may cause the switch to Th2 in severe hypercholesterolaemia.

Mycobacteria and other environmental organisms as immunomodulators for immunoregulatory disorders

In the rich, developed parts of the world there has been a steady and simultaneous increase in at least three groups of disease: (1) allergies, (2) inflammatory bowel diseases (IBD; e.g. Crohn's disease and ulcerative colitis) and (3) autoimmunity (e.g. type 1 diabetes and multiple sclerosis). Because the medical world is so compartmentalised it was some time before the connection between these increases was noticed and understood. There is now evidence that the simultaneous increase in these diseases of immunodysregulation is at least partly attributable to malfunction of regulatory T cells (Treg). This paper provides an overview of relevant work in each of these fields of medicine (though with emphasis on the allergic disorders), and concludes that the increasing failure of Treg is a consequence of diminished exposure to certain micro-organisms that are "old friends", because of their continuous presence throughout mammalian evolution. These organisms, which include saprophytic mycobacteria, helminths and lactobacilli, are recognised by the innate immune system as harmless, and as adjuvants for Treg induction. Polymorphisms of components of the innate immune system such as TLR2 and NOD2 appear to define subsets of the population that will develop immunoregulatory disorders when living in the modern environment. A further role of the "old friends" and of the Treg that they induce might be to maintain the levels of regulatory IL-10 secreting macrophages and antigen-presenting cells, which are depleted in asthma and Crohn's disease. These concepts are leading to novel therapies based on harmless organisms or their components. Phase I/II clinical trials have yielded some statistically significant results, and phase II trials are in progress.

The Roles of Cytokines, Inflammation and Immunity in Vascular Diseases

Recent findings regarding the roles of cytokines, inflammation and immunity during the development of atherosclerosis were reviewed. Especially, the relationships among pro-inflammatory cytokines such as interleukin (IL)-1, IL-18 and osteopontin, and anti-inflammatory cytokines such as IL-1 receptor antagonist, IL-10 and IL-18 binding protein to inflammation and atherosclerosis were investigated and are described in detail. In addition, helicobacter pylori and C pneumoniae infections to inflammations regarding the persistence of inflammation have been pointed out. A pro-inflammatory genotype or haplotype and toll-like receptors have been shown to be involved in human atherosclerosis. Atherosclerosis might therefore be a specific form of the chronic inflammatory process. In addition to hyperlipidemia, infections, cytokines and immunity might also be involved in the development of atherosclerosis. Certain treatments that reduce coronary risk also limit inflammation. Statins possess multiple pleiotropic effects such as an anti-inflammatory effect in addition to a lipid-lowering effect.

Angiotensin II-accelerated atherosclerosis and aneurysm formation is attenuated in osteopontin-deficient mice

Osteopontin (OPN) is expressed in atherosclerotic lesions, particularly in diabetic patients. To determine the role of OPN in atherogenesis, ApoE-/-OPN+/+, ApoE-/-OPN+/-, and ApoE-/-OPN-/- mice were infused with Ang II, inducing vascular OPN expression and accelerating atherosclerosis. Compared with ApoE-/-OPN+/+ mice, ApoE-/-OPN+/- and ApoE-/-OPN-/- mice developed less Ang II-accelerated atherosclerosis. ApoE-/- mice transplanted with bone marrow derived from ApoE-/-OPN-/- mice had less Ang II-induced atherosclerosis compared with animals receiving ApoE-/-OPN+/+ cells. Aortae from Ang II-infused ApoE-/-OPN-/- mice expressed less CD68, C-C-chemokine receptor 2, and VCAM-1. In response to intraperitoneal thioglycollate, recruitment of leukocytes in OPN-/- mice was impaired, and OPN-/- leukocytes exhibited decreased basal and MCP-1-directed migration. Furthermore, macrophage viability in atherosclerotic lesions from Ang II-infused ApoE-/-OPN-/- mice was decreased. Finally, Ang II-induced abdominal aortic aneurysm formation in ApoE-/-OPN-/- mice was reduced and associated with decreased MMP-2 and MMP-9 activity. These data suggest an important role for leukocyte-derived OPN in mediating Ang II-accelerated atherosclerosis and aneurysm formation.

Specific abrogation of transforming growth factor-beta signaling in T cells alters atherosclerotic lesion size and composition in mice

A large body of evidence supports a role for proinflammatory mediators in atherosclerotic disease progression and instability. However, only few endogenous mechanisms have been suggested that could alter disease progression. One such mechanism is thought to be mediated by transforming growth factor beta (TGF-beta). Transgenic mice that express a dominant-negative TGF-beta receptor type II under a T-cell-specific promoter were generated. Bone marrow transplantation from transgenic mice into irradiated low density lipoprotein receptor knock-out (LDLr KO) mice, subsequently fed an atherogenic diet, resulted in T-cell-specific blockade of TGF-beta signaling in the recipient mice and increased differentiation of T cells toward both T helper 1 (Th1) and Th2 phenotypes. These mice showed a significant decrease in atherosclerotic lesion size in the aortic sinus compared with mice receiving transplants with the wild-type bone marrow. Atherosclerotic plaques of mice receiving transplants with the transgenic bone marrow showed increased T-cell infiltration and expression of major histocompatability complex (MHC) class II, along with a decrease in smooth muscle cell and collagen content, a plaque phenotype that is potentially vulnerable to rupture. These results identify for the first time an important role for specific and selective T-cell-TGF-beta signaling in atherosclerosis.

Role of monocytes in atherogenesis

This review focuses on the role of monocytes in the early phase of atherogenesis, before foam cell formation. An emerging consensus underscores the importance of the cellular inflammatory system in atherogenesis. Initiation of the process apparently hinges on accumulating low-density lipoproteins (LDL) undergoing oxidation and glycation, providing stimuli for the release of monocyte attracting chemokines and for the upregulation of endothelial adhesive molecules. These conditions favor monocyte transmigration to the intima, where chemically modified, aggregated, or proteoglycan- or antibody-complexed LDL may be endocytotically internalized via scavenger receptors present on the emergent macrophage surface. The differentiating monocytes in concert with T lymphocytes exert a modulating effect on lipoproteins. These events propagate a series of reactions entailing generation of lipid peroxides and expression of chemokines, adhesion molecules, cytokines, and growth factors, thereby sustaining an ongoing inflammatory process leading ultimately to lesion formation. New data emerging from studies using transgenic animals, notably mice, have provided novel insights into many of the cellular interactions and signaling mechanisms involving monocytes/macrophages in the atherogenic processes. A number of these studies, focusing on mechanisms for monocyte activation and the roles of adhesive molecules, chemokines, cytokines and growth factors, are addressed in this review.

Chemistry and biology of angiitis inducer, Candida albicans water-soluble mannoprotein-beta-glucan complex (CAWS)

Deep mycoses have been clearly demonstrated to release beta-glucans into the blood. Structure of the beta-glucan was, at least in part, suggested to be a mannoprotein beta-glucan complex (CAWS) as assessed by biochemical and immunochemical analyses of the extracellular macromolecular fraction of Candida albicans. Half clearance time of i.v. administered CAWS was about 30 min in mice. In addition to the reactivity with limulus G-test, CAWS was found to exhibit various biological activities, such as cytokine synthesis by leukocyte, platelet aggregation, lethal toxicity, enhancement of side effect of indomethacin, induction of coronary arteritis in mice, and so on. In this review, the chemical properties and biological activities of CAWS are discussed.

Influence of aspirin on inflammatory markers in patients after acute myocardial infarction

The aim of this study was to assess the influence of aspirin on selected inflammatory markers in patients recovering from acute myocardial infarction (AMI). Patients participating in the Warfarin Aspirin Re-Infarction Study-II were randomized to either aspirin 160 mg/day or aspirin 75 mg/day + warfarin, or warfarin alone after AMI. After AMI, aspirin 160 mg/day was associated with significantly lower levels of high-sensitivity C-reactive protein and tumor necrosis factor-alpha than warfarin alone over 4 years. However, the same levels were not predictors for clinical end points.

Advances in retroviral transduction of hematopoietic stem cells for the gene therapy of atherosclerosis

PURPOSE OF REVIEW

Atherosclerosis is a chronic inflammatory disease that is the primary cause of morbidity and mortality in the developed world. Many studies have shown that macrophages and T-cells play critical roles in multiple aspects of the pathogenesis of the disease. Given that these cells are ultimately derived from bone marrow precursors, the concept of performing gene therapy for atherosclerosis through the retroviral transduction of hematopoietic stem cells has received much attention. This review will highlight recent advances that will help bring this goal closer.

RECENT FINDINGS

The clinical application of retroviral gene transfer into hematopoietic stem cells has been hampered, in part, by the absence of vectors that can direct long-lasting, cell-type specific gene expression. In this review we will detail recent developments in the design of novel retroviral and lentiviral vectors that appear to overcome these problems, offering approaches to express therapeutic genes in specific cell-types within atherosclerotic lesions. We will also highlight advances in our understanding of the pathogenesis of atherosclerosis that may offer new gene therapeutic targets.

SUMMARY

The use of retroviral transduction of hematopoietic stem cells for treatment of patients with atherosclerosis still remains a long-term goal. However, the recent development of retroviral vectors capable of directing expression to specific cell types within the lesion will allow more targeted therapeutic strategies to be devised. In addition, these vectors will provide powerful experimental tools to further our understanding of the pathogenesis of the disease.

Phenotypic and functional characterization of blood gammadelta T cells in sleep apnea

Hypoxia-induced lymphocyte dysfunction may be implicated in endothelial cell damage in obstructive sleep apnea (OSA) syndrome. gammadelta T cells' unique migration, cytotoxic features, and accumulation in atherosclerotic plaques are considered critical in cardiovascular disorders. We characterized the phenotype, cytokine profile, adhesion properties, and cytotoxicity of gammadelta T cells in patients with OSA and control subjects. The following is a summary of our major findings regarding OSA gammadelta T cells: (1) a significant increase in the expression of the inhibitory natural killer B1 receptors was found; (2) the intracellular content of proinflammatory cytokines tumor necrosis factor (TNF)-alpha and interleukin-8 was increased, and the content of the antiinflammatory cytokine interleukin-10 was decreased; (3) gammadelta T cells of patients with OSA adhered significantly more avidly to nonactivated endothelial cells in culture than those of control subjects; (4) L-selectin expression was higher; (5) anti-E/P-selectin antibodies and anti-TNF-alpha antibodies decreased the adhesion index of OSA gammadelta T lymphocytes/endothelial cells but not of control subjects; and (6) cytotoxicity of OSA gammadelta T lymphocytes against endothelial cells in culture was 2.5-fold higher than that of control subjects and could be prevented by pretreatment with anti-TNF-alpha. Collectively these data implicate gammadelta T lymphocyte function in atherogenic sequelae in OSA.

Protective effect of the immunosuppressant sirolimus against aortic atherosclerosis in apo E-deficient mice

Atherosclerosis is a chronic inflammatory disease that develops in response to injury to the vessel wall, and is augmented by hypercholesterolemia. To further delineate the role of the immune system and local factors in this process, we assessed the effects of the immunosuppressant sirolimus (Rapamycin, RAPAMUNE, Wyeth, Collegeville, PA) on atherosclerosis in the apoE-deficient (apoE KO) mouse, a well-accepted model of cardiovascular disease. ApoE KO mice were fed a high fat diet and sirolimus was administered. After 12 weeks, atherosclerotic lesions and plasma lipoproteins were measured. The expression of cytokines associated with atherosclerosis was also examined. All groups demonstrated plasma total cholesterol (TC) >1100 mg/dL. Sirolimus treatment was associated with a 30% increase in LDL-cholesterol (LDLc) and a dose-dependent elevation in HDL-cholesterol (HDLc). Despite increased LDLc, aortic atherosclerosis was markedly reduced in all sirolimus-treated groups. Sirolimus treatment resulted in decreased expression of IL-12p40, IFN-gamma and IL-10 mRNA. In contrast, TGF-beta1 was elevated. Sirolimus significantly reduced atherosclerosis in apo E-KO mice; this effect is independent of, and obviates, elevated plasma TC and LDLc. Sirolimus might therefore be of benefit on atherosclerosis in patients undergoing therapy, independent of any impact on circulating lipids.

Fenofibrate, a peroxisome proliferator-activated receptor alpha activator, suppresses experimental autoimmune myocarditis by stimulating the interleukin-10 pathway in rats

Experimental autoimmune myocarditis (EAM) in rats is an animal model of human giant cell myocarditis and postmyocarditis dilated cardiomyopathy. As the heart consumes large amounts of energy, heart diseases such as myocarditis and dilated cardiomyopathy are associated with abnormal fatty acid metabolism. Peroxisome proliferator-activated receptor alpha (PPARalpha) is a regulator of the oxidative degradation of fatty acids. To investigate the role of PPARalpha in EAM, fenofibrate (a PPARalpha activator) was administered to rats with EAM for 4 weeks. Reductions in the ratios of both ventricular weight to body weight and the area of inflammatory lesions to the total area of heart sections were observed in fenofibrate-treated rats when compared with controls. Fenofibrate ameliorated changes in serum albumin and sialic acid, which are markers of inflammation. Cardiac expression of interleukin-10 (IL-10) mRNA was more pronounced in the fenofibrate group than in the control group (1.3 +/- 0.2 vs 0.7 +/- 0.1; p < 0.01), and the area of intact myocardium correlated with the IL-10 mRNA level (p = 0.0297, r = 0.620). We suggest that PPARalpha activators may prevent the progression of myocarditis through increased expression of the gene encoding the anti-inflammatory cytokine IL-10, although the mechanisms involved remain to be determined.

Interleukins in atherosclerosis: molecular pathways and therapeutic potential

Interleukins are considered to be key players in the chronic vascular inflammatory response that is typical of atherosclerosis. Thus, the expression of proinflammatory interleukins and their receptors has been demonstrated in atheromatous tissue, and the serum levels of several of these cytokines have been found to be positively correlated with (coronary) arterial disease and its sequelae. In vitro studies have confirmed the involvement of various interleukins in pro-atherogenic processes, such as the up-regulation of adhesion molecules on endothelial cells, the activation of macrophages, and smooth muscle cell proliferation. Furthermore, studies in mice deficient or transgenic for specific interleukins have demonstrated that, whereas some interleukins are indeed intrinsically pro-atherogenic, others may have anti-atherogenic qualities. As the roles of individual interleukins in atherosclerosis are being uncovered, novel anti-atherogenic therapies, aimed at the modulation of interleukin function, are being explored. Several approaches have produced promising results in this respect, including the transfer of anti-inflammatory interleukins and the administration of decoys and antibodies directed against proinflammatory interleukins. The chronic nature of the disease and the generally pleiotropic effects of interleukins, however, will demand high specificity of action and/or effective targeting to prevent the emergence of adverse side effects with such treatments. This may prove to be the real challenge for the development of interleukin-based anti-atherosclerotic therapies, once the mediators and their targets have been delineated.

Association of low interleukin-10 levels with the metabolic syndrome in obese women

The potential role of anti-inflammatory cytokines in human obesity is unknown. We tested the hypothesis that low serum IL-10 concentrations associate with the metabolic syndrome in obese women. Compared with 50 matched nonobese women, the prevalence of the metabolic syndrome (>/=3 of the following abnormalities: waist circumference, >88 cm; triglycerides, >1.69 mmol/liter; high density lipoprotein cholesterol, <1.29 mmol/liter; blood pressure, >130/85 mm Hg; glucose, >6.1 mmol/liter) was higher in 50 obese women (52% vs. 16%; P < 0.01). As a group, obese women had higher circulating levels of IL-6, C-reactive protein, and IL-10 than nonobese women. In both obese and nonobese women, IL-10 levels were lower in those with than in women without the metabolic syndrome: obese, 1.3 (0.7/2.1) pg/ml vs. 4.5 (4.3/7.4) pg/ml (median and quartiles; P < 0.01); and nonobese, 0.9 (0.7/1.3) pg/ml vs. 1.3 (0.9/3.3) pg/ml (P < 0.05). After 12 months of a lifestyle program, body weight decreased by 10.9 +/- 1.7 kg and was associated with a significant decrement of IL-6, C-reactive protein, and IL-10 levels; the decrease in IL-10 levels was confined to obese women without the metabolic syndrome. These results show that circulating levels of the anti-inflammatory cytokine IL-10 are elevated in obese women and that low IL-10 levels are associated with the metabolic syndrome.

Carvedilol modulates in-vitro granulocyte-macrophage colony-stimulating factor-induced interleukin-10 production in U937 cells and human monocytes

Both granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-10 (IL-10) are important mediators regulating inflammatory responses. Inflammatory processes have an important role in atherogenesis. In this paper, the effects of carvedilol on GM-CSF-induced IL-10 production were examined on human monocytic cell line, U937, and purified human monocytes. First, we showed that one-time carvedilol pretreatment at concentrations 0.3-10 microM dose-dependently inhibited GM-CSF-induced IL-10 production in U937 cells. In addition, we found carvedilol to be non-cytotoxic at concentrations equal to or less than 10 microM. However, at concentrations higher than 10 microM, carvedilol induced programmed cell death in U937 cells. The inhibition of GM-CSF-induced IL-10 production by carvedilol was also observed at the expression of mRNA. Furthermore, the inhibition of IL-10 production was demonstrated in GM-CSF-activated purified human peripheral blood monocytes. Finally, long-term carvedilol pretreatment of U937 cells up to 2 months at concentrations of 1.0 microM mildly enhanced the IL-10 production. Our observations that carvedilol modulated GM-CSF-induced IL-10 production may have some implication in understanding the broad-spectrum effects of carvedilol in regulating inflammatory reactions.

Interleukin-10 expression after intramuscular DNA electrotransfer: kinetic studies

Transfected muscle can be used as a secreting tissue for therapeutic proteins. Skeletal muscle transfection is increased by suitable electric pulse application (electrotransfer). We and others had shown that electrotransfer of interleukin-10 encoding plasmid is an effective strategy in animal models of chronic diseases such as myocarditis, atherosclerosis, or rheumatoid arthritis. In the present work, we have studied murine interleukin-10 production and secretion after i.m. electrotransfer. In immunocompetent mice, serum and muscle mIL-10 levels were enhanced by electrotransfer. Serum mIL-10 concentration reached rapidly a peak level 2 days after electrotransfer. It then decreased to background at day 14. Muscle mIL-10 mRNA and protein remained more stable, being detectable up to 84 days after electrotransfer. A boost reinjection led to similar high level of circulating mIL-10. The fast decrease of serum mIL-10 was not observed in SCID mice.

Inflammatory imbalance between IL-10 and TNFalpha in unstable angina potential plaque stabilizing effects of IL-10

BACKGROUND

The pathogenesis of atherosclerosis and acute coronary syndromes involves inflammation and immunological mechanisms. We hypothesized that patients with unstable angina may have an imbalance between inflammatory and anti-inflammatory cytokines.

DESIGN

Plasma levels of tumour necrosis factor (TNF)alpha and interleukin (IL)-10 were analyzed in 44 patients with stable angina, 29 patients with unstable angina and 20 controls. mRNA levels of these cytokines were analyzed in peripheral blood mononuclear cells (PBMC). We also studied the in vitro effects of IL-10 in PBMC from unstable angina patients.

RESULTS

Our main findings were: (1) the angina patients and particularly those with unstable disease had significantly raised TNFalpha in comparison with the controls, both at the protein and mRNA level; (2) in contrast, the levels of IL-10 were not different in the angina patients in comparison with the healthy controls, resulting in a markedly enhanced TNFalpha:IL-10 ratio, particularly in the unstable angina patients; (3) while exogenously added IL-10 markedly inhibited the release of TNFalpha, IL-8 and tissue factor as well as impairing the gelatinolytic activity and mRNA production of matrix metalloproteinase-9, it enhanced the tissue inhibitor of this metalloproteinase (i.e. TIMP-1) in PBMC from the unstable angina patients.

CONCLUSION

Patients with unstable angina appear to have an imbalance between TNFalpha and IL-10, possibly favouring inflammatory net effects. IL-10 may have beneficial effects on mechanisms that are important in plaque rupture and thrombus formation.

Procoagulant and inflammatory response of virus-infected monocytes

BACKGROUND

Monocytes play a prominent role in inflammation, coagulation and atherosclerosis by their ability to produce tissue factor (TF) and cytokines. The aim of the present study was to establish whether virus-infected monocytes initiate coagulation. In addition, the production of cytokines by monocytes may accelerate the chronic process of atherosclerosis and may contribute to coronary syndromes by eliciting plaque instability.

MATERIALS AND METHODS

Monocytes were isolated by Vacutainer(R), BD Biosciences, Alphen aan den Rijn, Netherlands and subsequent magnetic cell sorting (MACS(R), Milteny Biotec, Bergish Gladbach, Germany). Coagulation times in normal pooled plasma and Factor VII-deficient plasma were measured after infection with cytomegalovirus (CMV), Chlamydia pneumoniae (Cp) and influenza A\H1N1. Anti-TF antibodies were added to neutralize TF expressed on monocytes. Interleukins (IL) 6, 8 and 10 were measured in the supernatants.

RESULTS

Chlamydia pneumoniae- and CMV-infected monocytes decreased the clotting time by 60%, and influenza-infected monocytes by 19%, as compared to uninfected monocytes. Procoagulant activity was absent when Factor VII-deficient plasma or anti-TF antibodies were used. Monocytes produced both IL-6 and IL-8 after infection with CMV (317 pg mL-1 and 250 pg mL-1) or Cp (733 pg mL-1 and 268 pg mL-1). Similar results were obtained for influenza virus-infected monocytes, but the levels of both cytokines were 3-5-fold higher (1797 pg mL-1 and 725 pg mL-1). Interleukin-10 was not produced by infected monocytes.

CONCLUSION

The procoagulant activity of virus-infected monocytes is TF-dependent. Although influenza infection did not generate a significant reduction in clotting time, the pronounced expression of IL-6 and IL-8 may induce local and/or systemic inflammatory reactions, which may be associated with plaque rupture and atherosclerosis. The lack of production of the anti-inflammatory cytokine IL-10 may even accelerate these processes.

T(H)2 predominant immune responses prevail in human abdominal aortic aneurysm

T lymphocytes localize within lesions of two diametrically opposed expressions of atherosclerosis: stenosis-producing plaques and ectasia-producing abdominal aortic aneurysm (AAA). T(H)1 immune responses appear to predominate in human stenotic lesions. However, little information exists regarding the nature of the T-cell infiltrate in AAAs. We demonstrate here that AAAs predominantly express T(H)2-associated cytokines and correspondingly lack mediators associated with the T(H)1 response as determined by Western blot and immunohistochemical analysis. In particular, aneurysmal tissue expressed interleukin (IL)-4, IL-5, and IL-10, cytokines not or only faintly detected in nondiseased tissue or stenotic atheroma. In contrast, AAAs contained low levels of the T(H)1 characteristic cytokines IL-2 and IL-15, which are amply expressed in stenotic lesions. Notably, stenotic lesions, but not AAAs, contained mature forms of the interferon-gamma-inducing cytokines IL-12 and IL-18 as well as the IL-18-processing enzyme caspase-1. Moreover, aneurysmal tissue lacked the receptor for interferon-gamma, although both types of lesions contained this T(H)1-promoting cytokine. These findings suggest that the functional repertoire of T cells differs in stenotic and aneurysmal lesions, and provide a novel framework for understanding the mechanisms of these diametrically opposite expressions of atherosclerosis.

[Interleukin-10 and coronary disease]

Understanding of the pathophysiology of atherosclerosis has changed markedly over the past few decades. It is now widely accepted that inflammation plays a fundamental role in the genesis and development of atherosclerosis. Inflammatory mechanisms also appear to determine clinical presentation and disease outcome. Atherosclerotic lesions have high concentrations of inflammatory cells (T lymphocytes and activated macrophages) as well as an abundance of pro-inflammatory cytokines [interleukin (IL)-1, IL-6, IL-8, interferon-gamma, tumor necrosis factor-alpha, etc.] that modulate local inflammatory responses. These may also alter plaque stability and facilitate the development of acute cardiovascular events. The role of anti-inflammatory cytokines in this context remains to be studied. IL-10 is an anti-inflammatory cytokine synthesised by T-lymphocytes and macrophages and has other anti-inflammatory effects. IL-10 expression within human atherosclerotic plaques has been demonstrated and animal experiments have shown that low levels of IL-10 lead to the development of extensive and unstable atherosclerotic lesions. Currently available evidence suggests a potential protective role for IL-10 in atherosclerosis. This new perspective on coronary disease as a chronic inflammatory process may open new avenues for the management of ischemic heart disease.