Alain Tedgui

Adaptive immunity in atherosclerosis: mechanisms and future therapeutic targets

Chronic inflammation drives the development of atherosclerosis, and adaptive immunity is deeply involved in this process. Initial studies attributed a pathogenic role to T cells in atherosclerosis, mainly owing to the proatherogenic role of the T-helper (TH)-1 cell subset, whereas the influence of TH2 and TH17 subsets is still debated. Today we know that T regulatory cells play a critical role in the protection against atherosclerotic lesion development and inflammation. In contrast to T cells, B cells were initially considered to be protective in atherosclerosis, assumingly through the production of protective antibodies against oxidized LDL. This concept has now been refined and proatherogenic roles of certain mature B cell subsets have been identified. We review the current knowledge about the role of various lymphocyte subsets in the development and progression of atherosclerosis and highlight future targets for immunomodulatory therapy.

Oxidation-specific biomarkers, lipoprotein(a), and risk of fatal and nonfatal coronary events.

OBJECTIVES This study sought to assess whether oxidation-specific biomarkers are associated with an increased risk of coronary artery disease (CAD) events. BACKGROUND The relationship of a panel of oxidative biomarkers and lipoprotein(a) [Lp(a)] to CAD risk is not fully determined. METHODS A prospective case-control study nested in the EPIC (European Prospective Investigation of Cancer)-Norfolk cohort of 45- to 79-year-old apparently healthy men and women followed for approximately 6 years was designed. Cases consisted of participants in whom fatal or nonfatal CAD developed, matched by sex, age, and enrollment time with controls without CAD. Baseline levels of oxidized phospholipids on apolipoprotein B-100 particles and Lp(a) were measured in 763 cases and 1,397 controls. Their relationship to secretory phospholipase A(2) type IIA mass and activity, myeloperoxidase mass, and lipoprotein-associated phospholipase A(2) activity and association with CAD events were determined. RESULTS After adjusting for age, smoking, diabetes, low- and high-density lipoprotein cholesterol, and systolic blood pressure, the highest tertiles of oxidized phospholipids on apolipoprotein B-100 particles and Lp(a) were associated with a significantly higher risk of CAD events (odds ratios: 1.67 and 1.64, respectively; p < 0.001) compared with the lowest tertiles. The odds ratio of CAD events associated with the highest tertiles of oxidized phospholipids on apolipoprotein B-100 particles or Lp(a) was significantly potentiated (approximately doubled) by the highest tertiles of secretory phospholipase A(2) activity and mass but less so for myeloperoxidase and lipoprotein-associated phospholipase A(2) activity. The odds ratios for fatal CAD were higher than for the combined end point. After taking into account the Framingham Risk Score, c-index values progressively increased when oxidative biomarkers were added to the model. CONCLUSIONS This EPIC-Norfolk study links pathophysiologically related oxidation-specific biomarkers and Lp(a) with CAD events. Oxidation-specific biomarkers provide cumulative predictive value when added to traditional cardiovascular risk factors.

Periodontal microbiota and phospholipases: The Oral Infections and Vascular Disease Epidemiology Study (INVEST)

OBJECTIVE Periodontal infections have been linked to cardiovascular disease, including atherosclerosis, and systemic inflammation has been proposed as a possible mediator. Secretory phospholipase A2 (s-PLA2) and Lipoprotein-associated PLA2 (Lp-PLA2) are inflammatory enzymes associated with atherosclerosis. No data are available on the association between oral microbiota and PLA2s. We studied whether a relationship exists between periodontal microbiota and the activities of these enzymes. METHODS The Oral Infection and Vascular Disease Epidemiology Study (INVEST) collected subgingival biofilms and serum samples from 593 dentate men and women (age 68.7 ± 8.6 years). 4561 biofilm samples were collected in the two most posterior teeth of each quadrant (average 7/participant) for quantitative assessment of 11 bacterial species using DNA-DNA checkerboard hybridization. Mean concentration of s-PLA2 and activities of s-PLA2 and Lp-PLA2 were regressed on tertiles of etiologic dominance (ED). ED is defined as the level of presumed periodontopathic species/combined level of all eleven species measured, and represents the relative abundance of periodontopathic organisms. Analyses were adjusted for age, sex, race/ethnicity, education, smoking, BMI, diabetes, LDL cholesterol and HDL cholesterol, and systolic blood pressure. RESULTS Higher levels of s-PLA2 activity were observed across increasing tertiles of etiologic dominance (0.66 ± 0.04 nmol ml(-1) min(-1), 0.73 ± 0.04 nmol ml(-1) min(-1), 0.89 ± 0.04 nmol ml-1 min-1; p < 0.001), with also a trend of association between Lp-PLA2 activity and ED (p = 0.07), while s-PLA2 concentration was unrelated to ED. CONCLUSION Increasingly greater s-PLA2 activity at higher tertiles of etiologic dominance may provide a mechanistic explanatory link of the relationship between periodontal microbiota and vascular diseases. Additional studies investigating the role of s-PLA2 are needed.

Relationship of IgG and IgM autoantibodies and immune complexes to oxidized LDL with markers of oxidation and inflammation and cardiovascular events: results from the EPIC-Norfolk Study

Levels of IgG and IgM autoantibodies (AA) to malondialdehyde (MDA)-LDL and apoB-immune complexes (ICs) were measured in 748 cases and 1,723 controls in the EPIC-Norfolk cohort and their association to coronary artery disease (CAD) events determined. We evaluated whether AA and IC modify CAD risk associated with secretory phospholipase A2 (sPLA2) type IIA mass and activity, lipoprotein-associated PLA2 activity, lipoprotein (a) [Lp(a)], oxidized phospholipids on apoB-100 (OxPL/apoB), myeloperoxidase, and high sensitivity C-reactive protein. IgG ICs were higher in cases versus controls (P = 0.02). Elevated levels of IgM AA and IC were inversely associated with Framingham Risk Score and number of metabolic syndrome criteria (p range 0.02–0.001). In regression analyses adjusted for age, smoking, diabetes, LDL-cholesterol, HDL-cholesterol, and systolic blood pressure, the highest tertiles of IgG and IgM AA and IC were not associated with higher risk of CAD events compared with the lowest tertiles. However, elevated levels of IgM IC reduced the risk of Lp(a) (P = 0.006) and elevated IgG MDA-LDL potentiated the risk of sPLA2 mass (P = 0.018). This epidemiological cohort of initially healthy subjects shows that IgG and IgM AA and IC are not independent predictors of CAD events but may modify CAD risk associated with elevated levels of oxidative biomarkers.

Erythrocyte microparticles can induce kidney vaso-occlusions in a murine model of sickle cell disease

Patients with sickle cell disease suffer from painful crises associated with disseminated vaso-occlusions, increased circulating erythrocyte microparticles (MPs), and thrombospondin-1 (TSP1). MPs are submicron membrane vesicles shed by compromised or activated cells. We hypothesized that TSP1 mediates MP shedding and participates in vaso-occlusions. We injected TSP1 to transgenic SAD mice with sickle cell disease and characterized circulating phosphatidylserine+ MPs by FACS. TSP1 stimulated MPs in plasma and initiated vaso-occlusions within minutes. In vitro, TSP1 triggered rapid erythrocyte conversion into spicule-covered echinocytes, followed by MP shedding. MP shedding was recapitulated by peptides derived from the TSP1 carboxyterminus. We purified MPs shed by erythrocytes in vitro and administered them back to SAD mice. MPs triggered immediate renal vaso-occlusions. In vitro, MPs triggered the production of radical oxygen species by endothelial monolayers, favored erythrocyte adhesion, and induced endothelial apoptosis. MPs also compromised vasodilation in perfused microvessels. These effects were inhibited by saturating MP phosphatidylserine with annexin-V, or with inhibitors of endothelial ROS production. We conclude that TSP1 triggers erythrocyte MP shedding. These MPs induce endothelial injury and facilitate acute vaso-occlusive events in transgenic SAD mice. This work supports a novel concept that toxic erythrocyte MPs may connect sickle cell anemia to vascular disease.

Phospholipase A2 Enzymes, High-Dose Atorvastatin, and Prediction of Ischemic Events After Acute Coronary Syndromes

Background— Secretory phospholipase A2 (sPLA2) and lipoprotein-associated phospholipase A2 (Lp-PLA2) are enzyme biomarkers of increased cardiovascular risk and targets of emerging therapeutic agents. Their relationship to cardiovascular events in the setting of high-dose statin therapy compared with placebo in patients with acute coronary syndrome is not known. Methods and Results— sPLA2 and Lp-PLA2 mass and activity were measured in 2587 patients in the Myocardial Ischemia Reduction With Acute Cholesterol Lowering (MIRACL) trial at baseline and after 16 weeks of treatment with atorvastatin 80 mg/d or placebo. Baseline levels of sPLA2 and Lp-PLA2 mass and activity were not associated with the primary efficacy measure of the trial of death, myocardial infarction, or unstable angina. However, in the overall cohort, baseline sPLA2 mass predicted risk of death after multivariable adjustment (hazard ratio for 2-fold increase, 1.30; 95% confidence interval, 1.09–1.56; P=0.004). This association remained significant when examined separately in the placebo group but not in the atorvastatin group. Compared with placebo, atorvastatin reduced median sPLA2 mass (−32.1% versus −23.1%), sPLA2 activity (−29.5% versus −19.2%), Lp-PLA2 mass (−35.8% versus −6.2%), and Lp-PLA2 activity (−24.3% versus 5.4%; P<0.001 for all). Atorvastatin reduced the hazard of death associated with elevated sPLA2 mass and activity by ≈50%. Conclusions— sPLA2 mass independently predicts death during a 16-week period after acute coronary syndrome. High-dose atorvastatin significantly reduces sPLA2 and Lp-PLA2 mass and activity after acute coronary syndrome and mitigates the risk of death associated with sPLA2 mass. Atorvastatin may exert antiinflammatory effects on phospholipases that contribute to its therapeutic benefit after acute coronary syndrome.

Dissecting abdominal aortic aneurysm in Ang II-infused mice: suprarenal branch ruptures and apparent luminal dilatation.

AIMS In this work, we provide novel insight into the morphology of dissecting abdominal aortic aneurysms in angiotensin II-infused mice. We demonstrate why they exhibit a large variation in shape and, unlike their human counterparts, are located suprarenally rather than infrarenally. METHODS AND RESULTS We combined synchrotron-based, ultra-high resolution ex vivo imaging (phase contrast X-Ray tomographic microscopy) with in vivo imaging (high-frequency ultrasound and contrast-enhanced micro-CT) and image-guided histology. In all mice, we observed a tear in the tunica media of the abdominal aorta near the ostium of the celiac artery. Independently we found that, unlike the gradual luminal expansion typical for human aneurysms, the outer diameter increase of angiotensin II-induced dissecting aneurysms in mice was related to one or several intramural haematomas. These were caused by ruptures of the tunica media near the ostium of small suprarenal side branches, which had never been detected by the established small animal imaging techniques. The tear near the celiac artery led to apparent luminal dilatation, while the intramural haematoma led to a dissection of the tunica adventitia on the left suprarenal side of the aorta. The number of ruptured branches was higher in those aneurysms that extended into the thoracic aorta, which explained the observed variability in aneurysm shape. CONCLUSION Our results are the first to describe apparent luminal dilatation, suprarenal branch ruptures, and intramural haematoma formation in dissecting abdominal aortic aneurysms in mice. Moreover, we validate and demonstrate the vast potential of phase contrast X-ray tomographic microscopy in cardiovascular small animal applications.

Transforming growth factor-alpha mediates nuclear factor kappaB activation in strained arteries.

Mechanical factors regulate both blood vessel growth and the development and progression of vascular disease. Acting on apoptotic and inflammatory signaling, the transcription factor nuclear factor &kgr;B (NF-&kgr;B) is a likely mediator of these processes. Nevertheless, pressure-dependent NF-&kgr;B activation pathways remain mostly unknown. Here we report that high intraluminal pressure induces reactive oxygen species (ROS) in arteries and that inhibition of NADPH oxidase prevents both the generation of ROS and the activation of NF-&kgr;B associated with high pressure. We also identify the epidermal growth factor receptor (EGFR) as a ROS-dependent signaling intermediate. In arteries from EGFR mutant mice (waved-2), pressure fails to activate NF-&kgr;B. Moreover, using vessels from EGFR ligand-deficient mice, we show that transforming growth factor (TGF)-&agr;, but neither heparin-binding EGF-like growth factor nor epiregulin, transduces NF-&kgr;B activation by high pressure. Preventing the release of the active form of TGF-&agr; also abolishes NF-&kgr;B induction by strain. The role of TGF-&agr; signaling in vascular remodeling is substantiated in vivo; angiotensin II-induced activation of NF-&kgr;B and associated cell proliferation and wall thickening are much reduced in TGF-&agr;–mutant mice compared with wild-type, despite equivalent hypertension in both groups. Conversely, apoptotic cells are detected only in vessels from hypertensive TGF-&agr;–mutant mice, outlining the role of NF-&kgr;B in cell survival. Finally, the NF-&kgr;B activation pathway contrasts with that of extracellular signal-regulated kinase 1/2, which is activated by stretch through the EGFR but does not implicate TGF-&agr;. Hence, our data identify TGF-&agr; as a potential specific target to modulate mechanosensitive NF-&kgr;B activation and associated vascular remodeling.

Humoral and cellular immune responses in atherosclerosis: spotlight on B- and T-cells.

Despite more than 1 million basic and clinical investigation reports on the mechanism and clinical outcome of cardiovascular events, the pathogenesis of this multi factorial disease is still incompletely understood, which is illustrated by the fact that it is still the leading cause of death in the western world. Over the decades it has been well approved that in addition to lipid dysfunction and arterial lipid accumulation, inflammation and autoimmune responses are major factors in directing the initiation and progression of atherosclerosis, the underlying cause of cardiovascular diseases. Atherosclerosis involves both humoral and cellular compartments of innate and adaptive immunity making it a very complex disease. This review discusses the innate and adaptive immune responses in atherosclerosis, with a focus on T- and B-cell mediated processes.

Circulating procoagulant microparticles in acute pulmonary embolism: A case–control study

We investigated whether circulating procoagulant microparticles (CPMPs) contributed to hypercoagulability in 45 patients with acute pulmonary embolism (APE) and in 45 controls with and 45 controls without cardiovascular risk factors. Concentrations of CPMPs and platelet-derived microparticles (PMPs) were statistically significantly higher in patients with APE than in controls without cardiovascular risk factors. PMPs appeared to be the main source of procoagulant microparticle release in APE, but this correlation disappeared when APE patients were compared to controls with cardiovascular risk factors. CPMPs may have a role in venous thrombosis as mediators of cardiovascular risk factors.