Genetic inactivation of IL-1 signaling enhances atherosclerotic plaque instability and reduces outward vessel remodeling in advanced atherosclerosis in mice

Atherosclerotic Plaque Destabilization

Understanding the pathophysiology of atherogenesis and the progression of atherosclerosis have been major goals of cardiovascular research during the previous decades. However, the complex molecular and cellular mechanisms underlying plaque destabilization remain largely obscure. Here, we review how lesional cells undergo cell death and how failed clearance exacerbates necrotic core formation. Advanced atherosclerotic lesions are further weakened by the pronounced local activity of matrix-degrading proteases as well as immature neovessels sprouting into the lesion. To stimulate translation of the current knowledge of molecular mechanisms of plaque destabilization into clinical studies, we further summarize available animal models of plaque destabilization. Based on the molecular mechanisms leading to plaque instability, we outline the current status of clinical and preclinical trials to induce plaque stability with a focus on induction of dead cell clearance, inhibition of protease activity, and dampening of inflammatory cell recruitment.

Bone marrow deficiency of MCPIP1 results in severe multi-organ inflammation but diminishes atherogenesis in hyperlipidemic mice

Objective

MCPIP1 is a newly identified protein that profoundly impacts immunity and inflammation. We aim to test if MCPIP1 deficiency in hematopoietic cells results in systemic inflammation and accelerates atherogenesis in mice.

Approach and Results

After lethally irradiated, LDLR^−/− mice were transplanted with bone marrow cells from either wild-type or MCPIP1^−/− mice. These chimeric mice were fed a western-type diet for 7 weeks. We found that bone marrow MCPIP1^−/− mice displayed a phenotype similar to that of whole body MCPIP1^−/− mice, with severe systemic and multi-organ inflammation. However, MCPIP1^−/− bone marrow recipients developed >10-fold less atherosclerotic lesions in the proximal aorta than WT bone marrow recipients, and essentially no lesions in en face aorta. The diminishment in atherosclerosis in bone marrow MCPIP1^−/− mice may be partially attributed to the slight decrease in their plasma lipids. Flow cytometric analysis of splenocytes showed that bone marrow MCPIP1^−/− mice contained reduced numbers of T cells and B cells, but increased numbers of regulatory T cells, Th17 cells, CD11b+/Gr1+ cells and CD11b+/Ly6C^low cells. This overall anti-atherogenic leukocyte profile may also contribute to the reduced atherogenesis. We also examined the cholesterol efflux capability of MCPIP1 deficient macrophages, and found that MCPIP1deficiency increased cholesterol efflux to apoAI and HDL, due to increased protein levels of ABCA1 and ABCG1.

Conclusions

Hematopoietic deficiency of MCPIP1 resulted in severe systemic and multi-organ inflammation but paradoxically diminished atherogenesis in mice. The reduced atheroegensis may be explained by the decreased plasma cholesterol levels, the anti-atherogenic leukocyte profile, as well as enhanced cholesterol efflux capability. This study suggests that, while atherosclerosis is a chronic inflammatory disease, the mechanisms underlying atherogenesis-associated inflammation in arterial wall versus the inflammation in solid organs may be substantially different.

Interleukins and atherosclerosis: a dysfunctional family grows

Atherosclerosis is driven by the release of cytokines from macrophages, and the β isoform of interleukin-1 (IL-1β) is a prime suspect in disease progression. Freigang et al. (2013) now suggest that IL-1α, a close relative, is selectively induced by fatty acids independent of the inflammasome to promote vascular inflammation.

Molecular biology of atherosclerosis

At least 468 individual genes have been manipulated by molecular methods to study their effects on the initiation, promotion, and progression of atherosclerosis. Most clinicians and many investigators, even in related disciplines, find many of these genes and the related pathways entirely foreign. Medical schools generally do not attempt to incorporate the relevant molecular biology into their curriculum. A number of key signaling pathways are highly relevant to atherogenesis and are presented to provide a context for the gene manipulations summarized herein. The pathways include the following: the insulin receptor (and other receptor tyrosine kinases); Ras and MAPK activation; TNF-α and related family members leading to activation of NF-κB; effects of reactive oxygen species (ROS) on signaling; endothelial adaptations to flow including G protein-coupled receptor (GPCR) and integrin-related signaling; activation of endothelial and other cells by modified lipoproteins; purinergic signaling; control of leukocyte adhesion to endothelium, migration, and further activation; foam cell formation; and macrophage and vascular smooth muscle cell signaling related to proliferation, efferocytosis, and apoptosis. This review is intended primarily as an introduction to these key signaling pathways. They have become the focus of modern atherosclerosis research and will undoubtedly provide a rich resource for future innovation toward intervention and prevention of the number one cause of death in the modern world.

Lipopolysaccharide stimulates platelets through an IL-1β autocrine loop

LPS activates platelets through TLR4, aiding productive sepsis, with stimulated splicing and translation of stored heteronuclear pro-IL-1β RNA. Although the IL-1R type 1 (IL-1R1) receptor for IL-1 shares downstream components with the TLR4 receptor, platelets are not known to express IL-1R1, nor are they known to respond to this cytokine. We show by flow cytometry and Western blotting that platelets express IL-1R1, and that IL-1β and IL-1α stimulate heteronuclear I-1β splicing and translation of the newly made mRNA in platelets. Platelets also respond to the IL-1β they make, which is exclusively associated with shed microparticles. Specific blockade of IL-1R1 with IL-1R antagonist suppressed platelet stimulation by IL-1, so IL-1β stimulates its own synthesis in an autocrine signaling loop. Strikingly, IL-1R antagonist inhibition, pharmacologic or genetic suppression of pro-IL-1β processing to active cytokine by caspase-1, or blockade of de novo protein synthesis also blocked LPS-induced IL-1β mRNA production. Robust stimulation of platelets by LPS therefore also required IL-1β amplification. Activated platelets made IL-1β in vivo as IL-1β rapidly accumulated in occluded murine carotid arteries by posttranscriptional RNA splicing unique to platelets. We conclude that IL-1β is a platelet agonist, that IL-1β acts through an autocrine stimulatory loop, that an IL-1β autocrine loop is required to amplify platelet activation by LPS, and that platelets immobilized in occlusive thrombi are activated over time to produce IL-1β. IL-1 is a new platelet agonist that promotes its own synthesis, connecting thrombosis with immunity.

Cigarette smoke modulates vascular smooth muscle phenotype: implications for carotid and cerebrovascular disease

BACKGROUND

The role of smooth muscle cell (SMC) phenotypic modulation in the cerebral circulation and pathogenesis of stroke has not been determined. Cigarette smoke is a major risk factor for atherosclerosis, but potential mechanisms are unclear, and its role in SMC phenotypic modulation has not been established.

METHODS AND RESULTS

In cultured cerebral vascular SMCs, exposure to cigarette smoke extract (CSE) resulted in decreased promoter activity and mRNA expression of key SMC contractile genes (SM-α-actin, SM-22α, SM-MHC) and the transcription factor myocardin in a dose-dependent manner. CSE also induced pro-inflammatory/matrix remodeling genes (MCP-1, MMPs, TNF-α, IL-1β, NF-κB). CSE increased expression of KLF4, a known regulator of SMC differentiation, and siKLF4 inhibited CSE induced suppression of SMC contractile genes and myocardin and activation of inflammatory genes. These mechanisms were confirmed in vivo following exposure of rat carotid arteries to CSE. Chromatin immune-precipitation assays in vivo and in vitro demonstrated that CSE promotes epigenetic changes with binding of KLF4 to the promoter regions of myocardin and SMC marker genes and alterations in promoter acetylation and methylation.

CONCLUSION

CSE exposure results in phenotypic modulation of cerebral SMC through myocardin and KLF4 dependent mechanisms. These results provides a mechanism by which cigarette smoke induces a pro-inflammatory/matrix remodeling phenotype in SMC and an important pathway for cigarette smoke to contribute to atherosclerosis and stroke.

Cholesterol crystals and inflammation

Chronic vascular inflammation is regarded as a crucial aspect of cardiovascular disease. However, the elicitors of this inflammatory response in the vessel wall are currently not well understood. Excessive amounts of cholesterol, an abundant and fundamental lipid molecule in mammalian cells, can initiate the development and progression of atherosclerosis. Accumulation of cholesterol in early atherosclerotic lesions results in the formation of macrophage foam cells, and crystalline cholesterol is found as a characteristic of advanced atherosclerotic plaques. Cholesterol crystals can activate the NLRP3 inflammasome, a multimolecular signaling complex of the innate immune system, resulting in caspase-1 mediated activation and secretion of proinflammatory interleukin-1 family cytokines. Furthermore, crystalline cholesterol is believed to induce plaque rupture by physical disruption of the fibrous cap covering atherosclerotic lesions. Here we review the effect of cholesterol deposition and crystallization on inflammatory responses in cardiovascular diseases.

A Systems Biology Approach to Characterize Biomarkers for Blood Stasis Syndrome of Unstable Angina Patients by Integrating MicroRNA and Messenger RNA Expression Profiling

Blood stasis syndrome (BSS) has been considered to be the major type of syndromes in unstable angina (UA) patients. The aim of this study was to find the systems biology-based microRNA (miRNA) and mRNA expression biomarkers for BSS of UA. We identified 1081 mRNAs and 25 miRNAs differentially expressed between BSS of UA patients and healthy controls by microarrays. We used DAVID, miRTrail, and the protein-protein interactions method to explore the related pathways and networks of differentially expressed miRNAs and mRNAs. By combining the results of pathways and networks, we found that the upregulation of miR-146b-5p may induce the downregulation of CALR to attenuate inflammation and the upregulation of miR-199a-5p may induce the downregulation of TP53 to inhibit apoptosis in BSS of UA patients. The expression patterns of miR-146b-5p, miR-199a-5p, CALR, and TP53 were confirmed by qRT-PCR in an independent validation cohort including BBS of UA patients, non-BBS of UA patients, and healthy controls. miR-146b-5p, miR-199a-5p, CALR, and TP53 could be significant biomarkers of BSS of UA patients. The systems biology-based miRNA and mRNA expression biomarkers for the BSS of UA may be helpful for the further stratification of UA patients when deciding on interventions or clinical trials.

Beneficial effects of quinoline-3-carboxamide (ABR-215757) on atherosclerotic plaque morphology in S100A12 transgenic ApoE null mice

OBJECTIVE

There is an emerging widespread interest in the role of damage-associated molecular pattern molecules (DAMP) S100A8, S100A9 and S100A12 in cardiovascular and other diseases. In this study we tested the efficacy of ABR-215757, a S100 protein binding immuno-modulatory compound to stabilize atherosclerosis in transgenic ApoE null mice that express the human pro-inflammatory S100A12 protein within the smooth muscle cell (SM22α-S100A12).

METHODS

Twelve-week old S100A12 transgenic/ApoE(-/-) and WT/ApoE(-/-) mice were treated with ABR-21575 for 5 weeks and were analyzed 4 month later.

RESULTS

Surface plasmon resonance analysis demonstrated that S100A12 interacts with ABR-215757 in a zinc dependent manner in vitro. In vivo, ABR-215757 administration reduced features of advanced plaque morphology resulting in smaller necrotic cores, diminished intimal and medial vascular calcification, and reduced amount of infiltrating inflammatory cells. ABR-215757 normalized aortic expression of RAGE protein and normalized experimentally-induced delayed hypersensitivity. The effect of ABR-215757 was more prominent in ApoE(-/-) mice expressing S100A12 than in ApoE(-/-) animals lacking expression of human S100A12 protein.

CONCLUSION

Our data suggest that S100A12 is important for progression of atherosclerosis and can be targeted by the small molecule ABR-215757. The specific binding of quinoline-3-carboxamides to S100A12 attenuates S100A12-mediated features of accelerated murine atherosclerosis.

Th17 cells and IL-17 are involved in the disruption of vulnerable plaques triggered by short-term combination stimulation in apolipoprotein E-knockout mice

Considerable evidence indicates that type 1 T helper (Th1)- and Th17-mediated immune responses promote the formation of atherosclerotic plaques while that CD4(+)CD25(+)Foxp3(+) regulatory T cells (Tregs) have a protective effect. However, the functions of diverse CD4(+) lymphocyte subsets in plaque rupture remain poorly understood because of a shortage of satisfactory plaque rupture models. Here, we established a murine model of atherosclerotic plaque rupture using a high-fat diet and collar placement on the carotid artery, and triggered plaque rupture by short-term stimulation with a combination of lipopolysaccharide, phenylephrine injection and cold in apolipoprotein E-knockout (ApoE(-/-)) mice. We investigated the associations between Th1 cells, Th17 cells and Tregs and plaque rupture by PCR, flow cytometry, ELISA and immunohistochemistry. In total, 75% (18/24) of vulnerable plaques, but no stable plaques, showed rupture characteristics. The proportion of Th17 cells was increased among splenocytes after treatment, but the changes in the levels of Th1 cells and Tregs were not related to rupture. Furthermore, the treatment resulted in high levels of interleukin-17 (IL-17) in the serum and in the region of plaque rupture. In vitro, IL-17 increased the level of apoptosis, a major factor associated with plaque rupture, in cultured murine vascular smooth muscle cells. Th17 cells and IL-17 may be involved in the disruption of vulnerable plaques triggered by short-term stimulation with lipopolysaccharide, phenylephrine injection and cold in ApoE(-/-)mice.

Adenosine 2A receptor modulates inflammation and phenotype in experimental abdominal aortic aneurysms

Activation of the adenosine 2A receptor (A2AR) reduces inflammation in models of acute injury but contribution in development of chronic abdominal aortic aneurysms (AAAs) is unknown. Elastase perfusion to induce AAA formation in A2AR-knockout (A2ARKO) and C57BL6/J wild-type (WT) mice resulted in nearly 100% larger aneurysms in A2ARKO compared to WT at d 14 (P<0.05), with evidence of greater elastin fragmentation, more immune cell infiltration, and increased matrix metallatoproteinase (MMP) 9 expression (P<0.05). Separately, exogenous A2AR antagonism in elastase-perfused WT mice also resulted in larger aneurysms (P<0.05), while A2AR agonism limited aortic dilatation (P<0.05). Activated Thy-1.2(+) T lymphocytes from WT mice treated in vitro with A2AR antagonist increased cytokine production, and treatment with A2AR agonist decreased cytokine production (P<0.05 for all). Primary activated CD4(+) T lymphocytes from A2ARKO mice exhibited greater chemotaxis (P<0.05). A2AR antagonist increased chemotaxis of activated CD4(+) cells from WT mice in vitro, and A2AR agonist reduced this effect (P<0.05). A2AR activation attenuates AAA formation partly by inhibiting immune cell recruitment and reducing elastin fragmentation. These findings support augmenting A2AR signaling as a putative target for limiting aneurysm formation.

Sputum mediator profiling and relationship to airway wall geometry imaging in severe asthma

Background

Severe asthma is a heterogeneous disease and the relationship between airway inflammation and airway remodelling is poorly understood. We sought to define sputum mediator profiles in severe asthmatics categorised by CT-determined airway geometry and sputum differential cell counts.

Methods

In a single centre cross-sectional observational study we recruited 59 subjects with severe asthma that underwent sputum induction and thoracic CT. Quantitative CT analysis of the apical segment of the right upper lobe (RB1) was performed. Forty-one mediators in sputum samples were measured of which 21 mediators that were assessable in >50% of samples were included in the analyses.

Results

Independent of airway geometry, sputum MMP9 and IL-1β were elevated in those groups with a high sputum neutrophil count while sputum ICAM was elevated in those subjects with a low sputum neutrophil count. In contrast, sputum CCL11, IL-1α and fibrinogen were different in groups stratified by both sputum neutrophil count and airway geometry. Sputum CCL11 concentration was elevated in subjects with a low sputum neutrophil count and high luminal and total RB1 area, whereas sputum IL1α was increased in subjects with a high sputum neutrophil count and low total RB1 area. Sputum fibrinogen was elevated in those subjects with RB1 luminal narrowing and in those subjects with neutrophilic inflammation without luminal narrowing.

Conclusions

We have demonstrated that sputum mediator profiling reveals a number of associations with airway geometry. Whether these findings reflect important biological phenotypes that might inform stratified medicine approaches requires further investigation.

CXCL5 limits macrophage foam cell formation in atherosclerosis

The ELR(+)-CXCL chemokines have been described typically as potent chemoattractants and activators of neutrophils during the acute phase of inflammation. Their role in atherosclerosis, a chronic inflammatory vascular disease, has been largely unexplored. Using a mouse model of atherosclerosis, we found that CXCL5 expression was upregulated during disease progression, both locally and systemically, but was not associated with neutrophil infiltration. Unexpectedly, inhibition of CXCL5 was not beneficial but rather induced a significant macrophage foam cell accumulation in murine atherosclerotic plaques. Additionally, we demonstrated that CXCL5 modulated macrophage activation, increased expression of the cholesterol efflux regulatory protein ABCA1, and enhanced cholesterol efflux activity in macrophages. These findings reveal a protective role for CXCL5, in the context of atherosclerosis, centered on the regulation of macrophage foam cell formation.

Anti-inflammatory therapy in chronic disease: challenges and opportunities

A number of widespread and devastating chronic diseases, including atherosclerosis, type 2 diabetes, and Alzheimer's disease, have a pathophysiologically important inflammatory component. In these diseases, the precise identity of the inflammatory stimulus is often unknown and, if known, is difficult to remove. Thus, there is interest in therapeutically targeting the inflammatory response. Although there has been success with anti-inflammatory therapy in chronic diseases triggered by primary inflammation dysregulation or autoimmunity, there are considerable limitations. In particular, the inflammatory response is critical for survival. As a result, redundancy, compensatory pathways, and necessity narrow the risk:benefit ratio of anti-inflammatory drugs. However, new advances in understanding inflammatory signaling and its links to resolution pathways, together with new drug development, offer promise in this area of translational biomedical research.

Blocking interleukin-1 as a novel therapeutic strategy for secondary prevention of cardiovascular events

The inflammatory hypothesis of atherosclerosis postulates that inflammation within the plaque promotes plaque progression and complications. Interleukin-1 (IL-1) is a key pro-inflammatory cytokine responsible for the amplification of the inflammatory response following injury. Animal studies show that IL-1 blockade is effective in limiting atherosclerosis and atherothrombosis and improving outcomes in acute myocardial infarction and ischemic stroke. Preliminary data in patients with acute myocardial infarction, ischemic stroke, and heart failure are promising. A large secondary prevention trial with canakinumab in patients with prior acute myocardial infarction is currently ongoing. Many unanswered questions remain regarding the optimal use of IL-1 blockade and the preferred agent.

Effects of Interleukin-1β Inhibition With Canakinumab on Hemoglobin A1c, Lipids, C-Reactive Protein, Interleukin-6, and Fibrinogen

Background—

To test formally the inflammatory hypothesis of atherothrombosis, an agent is needed that reduces inflammatory biomarkers such as C-reactive protein, interleukin-6, and fibrinogen but that does not have major effects on lipid pathways associated with disease progression.

Methods and Results—

We conducted a double-blind, multinational phase IIb trial of 556 men and women with well-controlled diabetes mellitus and high cardiovascular risk who were randomly allocated to subcutaneous placebo or to subcutaneous canakinumab at doses of 5, 15, 50, or 150 mg monthly and followed over 4 months. Compared with placebo, canakinumab had modest but nonsignificant effects on the change in hemoglobin A1c, glucose, and insulin levels. No effects were seen for low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, or non–high-density lipoprotein cholesterol, although triglyceride levels increased ≈10% in the 50-mg ( P =0.02) and 150-mg ( P =0.03) groups. By contrast, the median reductions in C-reactive protein at 4 months were 36.4%, 53.0%, 64.6%, and 58.7% for the 5-, 15-, 50-, and 150-mg canakinumab doses, respectively, compared with 4.7% for placebo (all P values ≤0.02). Similarly, the median reductions in interleukin-6 at 4 months across the canakinumab dose range tested were 23.9%, 32.5%, 47.9%, and 44.5%, respectively, compared with 2.9% for placebo (all P ≤0.008), and the median reductions in fibrinogen at 4 months were 4.9%, 11.7%, 18.5%, and 14.8%, respectively, compared with 0.4% for placebo (all P values ≤0.0001). Effects were observed in women and men. Clinical adverse events were similar in the canakinumab and placebo groups.

Conclusions—

Canakinumab, a human monoclonal antibody that neutralizes interleukin-1β, significantly reduces inflammation without major effect on low-density lipoprotein cholesterol or high-density lipoprotein cholesterol. These phase II trial data support the use of canakinumab as a potential therapeutic method to test directly the inflammatory hypothesis of atherosclerosis.

Clinical Trial Registration—

URL: http://www.clinicaltrials.gov . Unique identifier: NCT00900146.

Effect of interleukin 1β inhibition in cardiovascular disease

PURPOSE OF REVIEW

Atherosclerosis is greatly influenced by inflammatory mediators at all phases. Recent studies have suggested a causal role of one such mediator, interleukin 1β (IL-1β), in the development of atherosclerotic vascular disease. This review highlights recent investigation of the role of IL-1β in atherosclerosis and the potential of its inhibition as a promising therapeutic strategy for the treatment of atherosclerotic vascular disease.

RECENT FINDINGS

Studies in animals have generally shown decreased atherosclerotic plaque burden in atherosclerosis-prone mice deficient in IL-1β and increased plaque in mice exposed to excess IL-1β. In humans, IL-1β was found in greater concentrations in atherosclerotic human coronary arteries compared with normal coronary arteries. Preclinical and clinical studies of IL-1β inhibition have shown efficacy in the treatment of several inflammatory disorders, suggesting that IL-1β may be a novel therapeutic target for anti-inflammatory therapy in atherosclerosis, such as coronary artery disease (CAD).

SUMMARY

IL-1β inhibition offers an interesting and biology-based opportunity to test the potential beneficial effects of an anti-inflammatory therapeutic strategy in patients with CAD. A large clinical trial evaluating the impact of IL-1β inhibition in CAD is ongoing and will be an important test of the inflammation hypothesis in CAD.

Systemic immune activation shapes stroke outcome

Stroke is a major cause of morbidity and mortality, and activation of the immune system can impact on stroke outcome. Although the majority of research has focused on the role of the immune system after stroke there is increasing evidence to suggest that inflammation and immune activation prior to brain injury can influence stroke risk and outcome. With the high prevalence of co-morbidities in the Western world such as obesity, hypertension and diabetes, pre-existing chronic 'low-grade' systemic inflammation has become a customary characteristic of stroke pathophysiology that needs to be considered in the search for new therapies. The importance of the immune system in stroke has been demonstrated in a number of ways, both experimentally and in the clinical setting. This review will focus on the effect of immune activation arising from systemic inflammatory conditions and infection, how it affects the incidence and outcomes of stroke, and the possible underlying mechanisms involved. This article is part of a Special Issue entitled 'Neuroinflammation in neurodegeneration and neurodysfunction'.

The biological role of inflammation in atherosclerosis

The concept of the involvement of inflammation in the pathogenesis of atherosclerosis has existed since the 1800s, stemming from sentinel pathologic observations made by Rudolf Virchow, Karl Rokitansky, and others. Our understanding of the complex role played by immune and inflammatory mediators in the initiation and progression of atherosclerosis has evolved considerably in the intervening years, and today, a dramatically evolved understanding of these processes has led to advances in both diagnostic and prognostic approaches, as well as novel treatment modalities targeting inflammatory and immune mediators. Therapeutic interventions working through multiple mechanisms involved in atheroma pathogenesis, such as statins, which both lower lipids and alter the inflammatory milieu in the vessel wall, hold promise for the future. In this brief review, we explore the biological role of inflammation in atherosclerosis, with a focus on cellular involvement in both acute and chronic inflammation, and outline novel biomarkers of inflammation and atherosclerosis with a particular focus on the potential application of these novel approaches in improving strategies for disease diagnosis and management.

Smooth muscle cell phenotypic switching in atherosclerosis

Smooth muscle cells (SMCs) possess remarkable phenotypic plasticity that allows rapid adaptation to fluctuating environmental cues, including during development and progression of vascular diseases such as atherosclerosis. Although much is known regarding factors and mechanisms that control SMC phenotypic plasticity in cultured cells, our knowledge of the mechanisms controlling SMC phenotypic switching in vivo is far from complete. Indeed, the lack of definitive SMC lineage-tracing studies in the context of atherosclerosis, and difficulties in identifying phenotypically modulated SMCs within lesions that have down-regulated typical SMC marker genes, and/or activated expression of markers of alternative cell types including macrophages, raise major questions regarding the contributions of SMCs at all stages of atherogenesis. The goal of this review is to rigorously evaluate the current state of our knowledge regarding possible phenotypes exhibited by SMCs within atherosclerotic lesions and the factors and mechanisms that may control these phenotypic transitions.

IL-1 and atherosclerosis: a murine twist to an evolving human story

Inflammation is a critical component of atherosclerosis. IL-1 is a classic proinflammatory cytokine that has been linked to atherosclerosis. A clinical trial has been launched in which an antibody specific for IL-1β is being studied for its effects on cardiovascular events in patients with atherosclerosis. In this issue of the JCI, Alexander et al. report that mice lacking the receptor for IL-1 unexpectedly have features of advanced atherosclerosis that suggest the atherosclerotic plaques may be less stable. These findings illustrate the complexity of inflammatory pathways in atherosclerosis and suggest the need for careful calibration of antiinflammatory approaches to atherosclerosis.