The 5-lipoxygenase pathway promotes pathogenesis of hyperlipidemia-dependent aortic aneurysm

Targeting Inflammatory Pathways in Atherosclerosis: Exploring New Opportunities for Treatment

PURPOSE OF THE REVIEW

This review discusses the molecular mechanisms involved in the immuno-pathogenesis of atherosclerosis, the pleiotropic anti-inflammatory effects of approved cardiovascular therapies and the available evidence on immunomodulatory therapies for atherosclerotic cardiovascular disease (ACVD). We highlight the importance of clinical and translational research in identifying molecular mechanisms and discovering new therapeutic targets.

RECENT FINDINGS

The CANTOS (Canakinumab Anti-Inflammatory Thrombosis Outcomes Study) trial was the first to demonstrate a reduction in cardiovascular (CV) risk with anti-inflammatory therapy, irrespective of serum lipid levels. ACVD is the leading cause of death worldwide. Although targeting principal risk factors significantly reduces CV risk, residual risk remains unaddressed. The immunological mechanisms underlying atherosclerosis represent attractive therapeutic targets. Several commonly used and non-primarily anti-inflammatory drugs (i.e. SGLT2i, and PCSK9i) exhibit pleiotropic properties. Otherwise, recent trials have investigated the blockade of primarily inflammatory compounds, trying to lower the residual risk via low-dose IL-2, PTPN22 and CD31 pathway modulation. In the era of precision medicine, modern approaches may explore new pharmacological targets, identify new markers of vascular inflammation, and evaluate therapeutic responses.

The causal relationship between smoking and thoracic aortic aneurysm: Evidence from Mendelian randomization analysis

The potential role of smoking as a risk factor for thoracic aortic aneurysm is still a subject of debate. Therefore, it is important to systematically investigate the causal relationship between smoking and thoracic aortic aneurysm using Mendelian randomization methods. Genetic data were obtained from genome-wide association studies using the inverse variance weighting method as the primary approach. A thorough sensitivity analysis was conducted to ensure the reliability of the findings. Instrumental variables were assessed using the F statistic, and meta-analysis was employed to assess the average genetic predictive effect between smoking and thoracic aortic aneurysm. Our Mendelian randomization study found a positive association between smoking and thoracic aortic aneurysm. The odds ratios (OR) in the inverse variance weighting method were OR = 1.23 (95% confidence interval [CI] = 1.00-1.51; P = .053) and OR = 2.07 (95% CI = 1.10-3.91; P = .024). Furthermore, meta-analyses consistently demonstrated a positive causal relationship between ferritin and myocardial infarction, although statistical significance was not observed. The analysis results did not indicate any horizontal pleiotropy. Despite the presence of heterogeneity, the Mendelian randomization analysis still yielded significant results. This study employed Mendelian randomization to establish a positive association between smoking levels and the risk of thoracic aortic aneurysm. The genetic evidence reveals a causal relationship between the two, offering new insights for future interventions targeting thoracic aortic aneurysms.

Discovering Inflammation in Atherosclerosis: Insights from Pathogenic Pathways to Clinical Practice

This comprehensive review explores the various scenarios of atherosclerosis, a systemic and chronic arterial disease that underlies most cardiovascular disorders. Starting from an overview of its insidious development, often asymptomatic until it reaches advanced stages, the review delves into the pathophysiological evolution of atherosclerotic lesions, highlighting the central role of inflammation. Insights into clinical manifestations, including heart attacks and strokes, highlight the disease's significant burden on global health. Emphasis is placed on carotid atherosclerosis, clarifying its epidemiology, clinical implications, and association with cognitive decline. Prevention strategies, lifestyle modifications, risk factor management, and nuanced antithrombotic treatment considerations are critical to managing cardiovascular complications, thus addressing a crucial aspect of cardiovascular health.

Meta-Analysis of Single-Cell RNA-Seq Data Reveals the Mechanism of Formation and Heterogeneity of Tertiary Lymphoid Organ in Vascular Disease

BACKGROUND

Tertiary lymphoid organs (TLOs) are ectopic lymphoid organs developed in nonlymphoid tissues with chronic inflammation, but little is known about their existence in different types of vascular diseases and the mechanism that mediated their development.

METHODS

To take advantage of single-cell RNA sequencing techniques, we integrated 28 single-cell RNA sequencing data sets containing 5 vascular disease models (atherosclerosis, abdominal aortic aneurysm, intimal hyperplasia, isograft, and allograft) to explore TLOs existence and environment supporting its growth systematically. We also searched Medline, Embase, PubMed, and Web of Science from inception to January 2022 for published histological images of vascular remodeling for histological evidence to support TLO genesis.

RESULTS

Accumulation and infiltration of innate and adaptive immune cells have been observed in various remodeling vessels. Interestingly, the proportion of such immune cells incrementally increases from atherosclerosis to intimal hyperplasia, abdominal aortic aneurysm, isograft, and allograft. Importantly, we uncovered that TLO structure cells, such as follicular helper T cells and germinal center B cells, present in all remodeled vessels. Among myeloid cells and lymphocytes, inflammatory macrophages, and T helper 17 cells are the major lymphoid tissue inducer cells which were found to be positively associated with the numbers of TLO structural cells in remodeled vessels. Vascular stromal cells also actively participate in vascular TLO genesis by communicating with myeloid cells and lymphocytes via CCLs (C-C motif chemokine ligands), CXCL (C-X-C motif ligand), lymphotoxin, BMP (bone morphogenetic protein) chemotactic, FGF-2 (fibroblast growth factor-2), and IGF (insulin growth factor) proliferation mechanisms, particularly for lymphoid tissue inducer cell aggregation. Additionally, the interaction between stromal cells and immune cells modulates extracellular matrix remodeling. Among TLO structure cells, follicular helper T, and germinal center B cells have strong interactions via TCR (T-cell receptor), CD40 (cluster of differentiation 40), and CXCL signaling, to promote the development and maturation of the germinal center in TLO. Consistently, by reviewing the histological images from the literature, TLO genesis was found in those vascular remodeling models.

CONCLUSIONS

Our analysis showed the existence of TLOs across 5 models of vascular diseases. The mechanisms that support TLOs formation in different models are heterogeneous. This study could be a valuable resource for understanding and discovering new therapeutic targets for various forms of vascular disease.

Bony Fish Arachidonic Acid 15-Lipoxygenases Exhibit Different Catalytic Properties than Their Mammalian Orthologs, Suggesting Functional Enzyme Evolution during Vertebrate Development

The human genome involves six functional arachidonic acid lipoxygenase (ALOX) genes and the corresponding enzymes (ALOX15, ALOX15B, ALOX12, ALOX12B, ALOXE3, ALOX5) have been implicated in cell differentiation and in the pathogenesis of inflammatory, hyperproliferative, metabolic, and neurological disorders. In other vertebrates, ALOX-isoforms have also been identified, but they occur less frequently. Since bony fish represent the most abundant subclass of vertebrates, we recently expressed and characterized putative ALOX15 orthologs of three different bony fish species (Nothobranchius furzeri, Pundamilia nyererei, Scleropages formosus). To explore whether these enzymes represent functional equivalents of mammalian ALOX15 orthologs, we here compared a number of structural and functional characteristics of these ALOX-isoforms with those of mammalian enzymes. We found that in contrast to mammalian ALOX15 orthologs, which exhibit a broad substrate specificity, a membrane oxygenase activity, and a special type of dual reaction specificity, the putative bony fish ALOX15 orthologs strongly prefer C20 fatty acids, lack any membrane oxygenase activity and exhibit a different type of dual reaction specificity with arachidonic acid. Moreover, mutagenesis studies indicated that the Triad Concept, which explains the reaction specificity of all mammalian ALOX15 orthologs, is not applicable for the putative bony fish enzymes. The observed functional differences between putative bony fish ALOX15 orthologs and corresponding mammalian enzymes suggest a targeted optimization of the catalytic properties of ALOX15 orthologs during vertebrate development.

Cardiovascular Brain Circuits

The cardiovascular system is hardwired to the brain via multilayered afferent and efferent polysynaptic axonal connections. Two major anatomically and functionally distinct though closely interacting subcircuits within the cardiovascular system have recently been defined: The artery-brain circuit and the heart-brain circuit. However, how the nervous system impacts cardiovascular disease progression remains poorly understood. Here, we review recent findings on the anatomy, structures, and inner workings of the lesser-known artery-brain circuit and the better-established heart-brain circuit. We explore the evidence that signals from arteries or the heart form a systemic and finely tuned cardiovascular brain circuit: afferent inputs originating in the arterial tree or the heart are conveyed to distinct sensory neurons in the brain. There, primary integration centers act as hubs that receive and integrate artery-brain circuit-derived and heart-brain circuit-derived signals and process them together with axonal connections and humoral cues from distant brain regions. To conclude the cardiovascular brain circuit, integration centers transmit the constantly modified signals to efferent neurons which transfer them back to the cardiovascular system. Importantly, primary integration centers are wired to and receive information from secondary brain centers that control a wide variety of brain traits encoded in engrams including immune memory, stress-regulating hormone release, pain, reward, emotions, and even motivated types of behavior. Finally, we explore the important possibility that brain effector neurons in the cardiovascular brain circuit network connect efferent signals to other peripheral organs including the immune system, the gut, the liver, and adipose tissue. The enormous recent progress vis-à-vis the cardiovascular brain circuit allows us to propose a novel neurobiology-centered cardiovascular disease hypothesis that we term the neuroimmune cardiovascular circuit hypothesis.

Novel mechanisms and therapeutic targets in atherosclerosis: inflammation and beyond

This review based on the ESC William Harvey Lecture in Basic Science 2022 highlights recent experimental and translational progress on the therapeutic targeting of the inflammatory components in atherosclerosis, introducing novel strategies to limit side effects and to increase efficacy. Since the validation of the inflammatory paradigm in CANTOS and COLCOT, efforts to control the residual risk conferred by inflammation have centred on the NLRP3 inflammasome-driven IL-1β-IL6 axis. Interference with the co-stimulatory dyad CD40L-CD40 and selective targeting of tumour necrosis factor-receptor associated factors (TRAFs), namely the TRAF6-CD40 interaction in macrophages by small molecule inhibitors, harbour intriguing options to reduce established atherosclerosis and plaque instability without immune side effects. The chemokine system crucial for shaping immune cell recruitment and homoeostasis can be fine-tuned and modulated by its heterodimer interactome. Structure-function analysis enabled the design of cyclic, helical, or linked peptides specifically targeting or mimicking these interactions to limit atherosclerosis or thrombosis by blunting myeloid recruitment, boosting regulatory T cells, inhibiting platelet activity, or specifically blocking the atypical chemokine MIF without notable side effects. Finally, adventitial neuroimmune cardiovascular interfaces in advanced atherosclerosis show robust restructuring of innervation from perivascular ganglia and employ sensory neurons of dorsal root ganglia to enter the central nervous system and to establish an atherosclerosis-brain circuit sensor, while sympathetic and vagal efferents project to the celiac ganglion to create an atherosclerosis-brain circuit effector. Disrupting this circuitry by surgical or chemical sympathectomy limited disease progression and enhanced plaque stability, opening exciting perspectives for selective and tailored intervention beyond anti-inflammatory strategies.

Genetic and Epigenetic Regulation of Lipoxygenase Pathways and Reverse Cholesterol Transport in Atherogenesis

Atherosclerosis is one of the most important medical and social problems of modern society. Atherosclerosis causes a large number of hospitalizations, disability, and mortality. A considerable amount of evidence suggests that inflammation is one of the key links in the pathogenesis of atherosclerosis. Inflammation in the vascular wall has extensive cross-linkages with lipid metabolism, and lipid mediators act as a central link in the regulation of inflammation in the vascular wall. Data on the role of genetics and epigenetic factors in the development of atherosclerosis are of great interest. A growing body of evidence is strengthening the understanding of the significance of gene polymorphism, as well as gene expression dysregulation involved in cross-links between lipid metabolism and the innate immune system. A better understanding of the genetic basis and molecular mechanisms of disease pathogenesis is an important step towards solving the problems of its early diagnosis and treatment.

Outcomes of reconstructive endovascular treatment of vertebrobasilar dissecting aneurysms with intramural hematoma

Background

Vertebrobasilar dissecting aneurysms (VBDAs) with an intramural hematoma (IMH) usually cause symptoms because of mass effect and grow in size over time. Clinical outcomes are generally poor.

Objective

This study aimed to examine outcomes of reconstructive endovascular treatment (EVT) in patients with VBDAs with IMH. Safety and effectiveness were compared between flow diverters (FDs) and conventional stents.

Methods

We retrospectively analyzed the clinical and radiological data of 36 VBDAs with IMH in 36 patients who underwent EVT with either FDs or conventional stents from January 2012 to December 2020 at our institution.

Results

Among the 36 study patients, 20 were treated with FDs and 16 with conventional stents. Incidence of procedure-related complications did not significantly differ between the two stents. IMH growth occurred after EVT in a significantly higher proportion of conventional stent group aneurysms (zero vs. 31.3% [5/16]; p = 0.012). Among the five aneurysms with IMHs that grew, all recurred. Change in IMH size after EVT was significantly lower in the FD group (−2.7 vs. +8.1%, p = 0.036). However, after the recurrent aneurysms were removed from the conventional stent group, change in IMH size did not significantly differ between the two groups (−2.7 vs. +1.0%, p = 0.332). The proportion of patients who experienced an improvement in mRS score after EVT was significantly higher in the FD group (60 vs. 25%, p = 0.036).

Conclusion

IMHs in VBDAs stop growing after successful reconstructive EVT. Although both FD and conventional stent treatment are effective, FD treatment may be superior based on clinical outcomes and effect on IMH size.

Targeting new N-furfurylated 4-chlorophenyl-1,2,4-triazolepropionamide hybrids as potential 15-lipoxygenase inhibitors supported with in vitro and in silico studies

Lipoxygenases (LOXs) are a group of enzymes that catalyze the oxidation of polyunsaturated fatty acids and initiate the biosynthesis of secondary metabolites that are involved to control inflammation. In search of new and more potent LOX inhibitors, a series of new 3-(5-(4-chlorophenyl)-4-(2-furylmethyl)-1,2,4-triazole hybrids was prepared and screened for its LOX inhibitory potential. 4-Chlorobenzoic acid (a) was metamorphosed into N-furfuryl-5-(4-chlorophenyl)-4-(2-furylmethyl)-1,2,4-triazole (4) via intermediates like benzoate (1), hydrazide (2) and semicarbazide (3). Finally, triazole (4) was fused with propionamides (6a-o) and transformed it into the aimed derivatives (7a-o). The structural interpretations of the prepared derivatives (7a-o) were accomplished via FTIR, ¹H-, ¹³C-NMR spectroscopy, EI-MS and HR-EI-MS spectrometry. The inhibitory potency of the compounds against soybean 15-LOX was determined by in vitro assay using chemiluminescence method. Compounds 7a and 7f exhibited potent LOX inhibitory profiles with IC₅₀ 21.83 ± 0.56 and 25.72 ± 0.51 µM, whereas 7d and 7e showed comparable inhibitory potential with IC₅₀ values of 34.52 ± 0.39 and 39.12 ± 0.46 µM, respectively. Compounds 7a, 7f, 7d and 7e exhibited 65.58 ± 1.4%, 54.72 ± 1.3%, 58.52 ± 1.2% and 63.56 ± 1.4% blood mononuclear cells viability, respectively. Density functional theory and molecular docking studies further strengthened the studies of the synthesized compounds and these derivatives perceived to be potential 'lead' compounds in drug discovery as anti-LOX.Communicated by Ramaswamy H. Sarma.

On vasa vasorum: A history of advances in understanding the vessels of vessels

The vasa vasorum are a vital microvascular network supporting the outer wall of larger blood vessels. Although these dynamic microvessels have been studied for centuries, the importance and impact of their functions in vascular health and disease are not yet fully realized. There is now rich knowledge regarding what local progenitor cell populations comprise and cohabitate with the vasa vasorum and how they might contribute to physiological and pathological changes in the network or its expansion via angiogenesis or vasculogenesis. Evidence of whether vasa vasorum remodeling incites or governs disease progression or is a consequence of cardiovascular pathologies remains limited. Recent advances in vasa vasorum imaging for understanding cardiovascular disease severity and pathophysiology open the door for theranostic opportunities. Approaches that strive to control angiogenesis and vasculogenesis potentiate mitigation of vasa vasorum-mediated contributions to cardiovascular diseases and emerging diseases involving the microcirculation.

Knock-In Mice Expressing a 15-Lipoxygenating Alox5 Mutant Respond Differently to Experimental Inflammation Than Reported Alox5-/- Mice

Arachidonic acid 5-lipoxygenase (ALOX5) is the key enzyme in the biosynthesis of pro-inflammatory leukotrienes. We recently created knock-in mice (Alox5-KI) which express an arachidonic acid 15-lipoxygenating Alox5 mutant instead of the 5-lipoxygenating wildtype enzyme. These mice were leukotriene deficient but exhibited an elevated linoleic acid oxygenase activity. Here we characterized the polyenoic fatty acid metabolism of these mice in more detail and tested the animals in three different experimental inflammation models. In experimental autoimmune encephalomyelitis (EAE), Alox5-KI mice displayed an earlier disease onset and a significantly higher cumulative incidence rate than wildtype controls but the clinical score kinetics were not significantly different. In dextran sodium sulfate-induced colitis (DSS) and in the chronic constriction nerve injury model (CCI), Alox5-KI mice performed like wildtype controls with similar genetic background. These results were somewhat surprising since in previous loss-of-function studies targeting leukotriene biosynthesis (Alox5^−/− mice, inhibitor studies), more severe inflammatory symptoms were observed in the EAE model but the degree of inflammation in DSS colitis was attenuated. Taken together, our data indicate that these mutant Alox5-KI mice respond differently in two models of experimental inflammation than Alox5^−/− animals tested previously in similar experimental setups.

Key Chemokine Pathways in Atherosclerosis and Their Therapeutic Potential

The search to improve therapies to prevent or treat cardiovascular diseases (CVDs) rages on, as CVDs remain a leading cause of death worldwide. Here, the main cause of CVDs, atherosclerosis, and its prevention, take center stage. Chemokines and their receptors have long been known to play an important role in the pathophysiological development of atherosclerosis. Their role extends from the initiation to the progression, and even the potential regression of atherosclerotic lesions. These important regulators in atherosclerosis are therefore an obvious target in the development of therapeutic strategies. A plethora of preclinical studies have assessed various possibilities for targeting chemokine signaling via various approaches, including competitive ligands and microRNAs, which have shown promising results in ameliorating atherosclerosis. Developments in the field also include detailed imaging with tracers that target specific chemokine receptors. Lastly, clinical trials revealed the potential of various therapies but still require further investigation before commencing clinical use. Although there is still a lot to be learned and investigated, it is clear that chemokines and their receptors present attractive yet extremely complex therapeutic targets. Therefore, this review will serve to provide a general overview of the connection between various chemokines and their receptors with atherosclerosis. The different developments, including mouse models and clinical trials that tackle this complex interplay will also be explored.

Non-syndromic thoracic aortic aneurysm: cellular and molecular insights

Thoracic aortic aneurysm (TAA) develops silently and asymptomatically and is a major cause of mortality. TAA prevalence is greatly underestimated, it is usually diagnosed incidentally, and its treatment consists mainly of prophylactic surgery based on the aortic diameter. The lack of effective drugs and biological markers to identify and stratify TAAs by risk before visible symptoms results from scant knowledge of its pathophysiological mechanisms. Here we integrate the structural impairment affecting non-syndromic non-familial TAA with the main cellular and molecular changes described so far and consider how these changes are interconnected through specific pathways. The ultimate goal is to define much-needed novel markers of TAA, and so the potential of previously identified molecules to aid in early diagnosis/prognosis is also discussed. © 2021 The Authors. The Journal of Pathology published by John Wiley & Sons, Ltd. on behalf of The Pathological Society of Great Britain and Ireland.

Trans triacylglycerols from dairy products and industrial hydrogenated oil exhibit different effects on the function of human umbilical vein endothelial cells via modulating phospholipase A2/arachidonic acid metabolism pathways

Dairy fat intake has been considered as a risk factor for cardiovascular disease. Rodent models show that trans fatty acids in industrial hydrogenated oil and ruminant milk have different effects on cardiovascular diseases. One of the main reasons is that the distributions of trans fatty acids in triacylglycerols from dairy products and from industrial hydrogenated oil are different, which affects lipid absorption and metabolism. This study investigated the effects of 1,3-olein-2-elaidin (OEO, representing industrial hydrogenated oil triacylglycerols) and 1-vaccenic-2,3-olein (OOV, representing ruminant triacylglycerols in dairy products) on the function of human umbilical vein endothelial cells (HUVEC), including cell viability, lactate dehydrogenase (LDH) exudation rate, and nitric oxide secretory and nitric oxide synthase relative activity. We found that the detrimental effect of OEO on HUVEC was significantly greater than that of OOV. The results also showed that the absorption rate of OEO in HUVEC (78.25%) was significantly greater than that of OOV (63.32%). Mechanistically, based on phospholipidomics analysis, we found that calcium-independent phospholipase A2 (iPLA2) played a key role with regard to the OOV-mediated arachidonic acid (ARA)/COX-2/PG pathway, whereas secretory phospholipase A2 (sPLA2) and cytoplasmic phospholipase A2 (cPLA2) are responsible for the OEO-mediated ARA/COX-2/PG pathway. Moreover, OEO had a greater effect on the protein expression of COX-2 and PG secretion than OOV. In addition, iPLA2, sPLA2, and cPLA2 could mediate the ARA/CYP4A11 pathway in OOV-treated HUVEC, but only iPLA2 could mediate this pathway in HUVEC treated with OEO. We also found that sPLA2 could mediate the ARA/5-LOX pathway in HUVEC treated with OOV, but none of these 3 forms of PLA2 could mediate this pathway in HUVEC treated with OEO. On the other hand, after OOV treatment, trans-11 C18:1 was converted to beneficial forms of fatty acids in HUVEC, including conjugated linoleic acid (CLA) and trans-9 C16:1. In conclusion, we elucidated the potential mechanisms that might account for the diverse effects of triacylglycerols from industrial hydrogenated oil and ruminant milk on the function of HUVEC.

Testosterone Metabolite 6β-Hydroxytestosterone Contributes to Angiotensin II-Induced Abdominal Aortic Aneurysms in Apoe-/- Male Mice

Background

Sex is a prominent risk factor for abdominal aortic aneurysms (AAAs), and angiotensin II (Ang II) induces AAA formation to a greater degree in male than in female mice. We previously reported that cytochrome P450 1B1 contributes to the development of hypertension, as well as AAAs, in male mice. We also found that a cytochrome P450 1B1‐generated metabolite of testosterone, 6β‐hydroxytestosterone (6β‐OHT), contributes to Ang II‐induced hypertension and associated cardiovascular and renal pathogenesis in male mice. The current study was conducted to determine the contribution of 6β‐OHT to Ang II‐induced AAA development in Apoe^–/– male mice.

Methods and Results

Intact or castrated Apoe^–/–/Cyp1b1^+/+ and Apoe^–/–/Cyp1b1^–/– male mice were infused with Ang II or its vehicle for 28 days, and administered 6β‐OHT every third day for the duration of the experiment. Abdominal aortas were then evaluated for development of AAAs. We observed a significant increase in the incidence and severity of AAAs in intact Ang II‐infused Apoe^–/–/Cyp1b1^+/+ mice, compared with vehicle‐treated mice, which were minimized in castrated Apoe^–/–/Cyp1b1^+/+ and intact Apoe^–/–/Cyp1b1^–/– mice infused with Ang II. Treatment with 6β‐OHT significantly restored the incidence and severity of AAAs in Ang II‐infused castrated Apoe^–/–/Cyp1b1^+/+ and intact Apoe^–/–/Cyp1b1^–/– mice. However, administration of testosterone failed to increase AAA incidence and severity in Ang II‐infused intact Apoe^–/–/Cyp1b1^–/– mice.

Conclusions

Our results indicate that the testosterone‐cytochrome P450 1B1‐generated metabolite 6β‐OHT contributes to Ang II‐induced AAA development in Apoe^–/– male mice.

Metabolism pathways of arachidonic acids: mechanisms and potential therapeutic targets

The arachidonic acid (AA) pathway plays a key role in cardiovascular biology, carcinogenesis, and many inflammatory diseases, such as asthma, arthritis, etc. Esterified AA on the inner surface of the cell membrane is hydrolyzed to its free form by phospholipase A2 (PLA2), which is in turn further metabolized by cyclooxygenases (COXs) and lipoxygenases (LOXs) and cytochrome P450 (CYP) enzymes to a spectrum of bioactive mediators that includes prostanoids, leukotrienes (LTs), epoxyeicosatrienoic acids (EETs), dihydroxyeicosatetraenoic acid (diHETEs), eicosatetraenoic acids (ETEs), and lipoxins (LXs). Many of the latter mediators are considered to be novel preventive and therapeutic targets for cardiovascular diseases (CVD), cancers, and inflammatory diseases. This review sets out to summarize the physiological and pathophysiological importance of the AA metabolizing pathways and outline the molecular mechanisms underlying the actions of AA related to its three main metabolic pathways in CVD and cancer progression will provide valuable insight for developing new therapeutic drugs for CVD and anti-cancer agents such as inhibitors of EETs or 2J2. Thus, we herein present a synopsis of AA metabolism in human health, cardiovascular and cancer biology, and the signaling pathways involved in these processes. To explore the role of the AA metabolism and potential therapies, we also introduce the current newly clinical studies targeting AA metabolisms in the different disease conditions.

Integrative analyses of TEDDY Omics data reveal lipid metabolism abnormalities, increased intracellular ROS and heightened inflammation prior to autoimmunity for type 1 diabetes

BACKGROUND

The Environmental Determinants of Diabetes in the Young (TEDDY) is a prospective birth cohort designed to study type 1 diabetes (T1D) by following children with high genetic risk. An integrative multi-omics approach was used to evaluate islet autoimmunity etiology, identify disease biomarkers, and understand progression over time.

RESULTS

We identify a multi-omics signature that was predictive of islet autoimmunity (IA) as early as 1 year before seroconversion. At this time, abnormalities in lipid metabolism, decreased capacity for nutrient absorption, and intracellular ROS accumulation are detected in children progressing towards IA. Additionally, extracellular matrix remodeling, inflammation, cytotoxicity, angiogenesis, and increased activity of antigen-presenting cells are observed, which may contribute to beta cell destruction. Our results indicate that altered molecular homeostasis is present in IA-developing children months before the actual detection of islet autoantibodies, which opens an interesting window of opportunity for therapeutic intervention.

CONCLUSIONS

The approach employed herein for assessment of the TEDDY cohort showcases the utilization of multi-omics data for the modeling of complex, multifactorial diseases, like T1D.

Targeting Leukotrienes as a Therapeutic Strategy to Prevent Comorbidities Associated with Metabolic Stress

Leukotrienes (LTs) are potent lipid mediators that exert a variety of functions, ranging from maintaining the tone of the homeostatic immune response to exerting potent proinflammatory effects. Therefore, LTs are essential elements in the development and maintenance of different chronic diseases, such as asthma, arthritis, and atherosclerosis. Due to the pleiotropic effects of LTs in the pathogenesis of inflammatory diseases, studies are needed to discover potent and specific LT synthesis inhibitors and LT receptor antagonists. Even though most clinical trials using LT inhibitors or antagonists have failed due to low efficacy and/or toxicity, new drug development strategies are driving the discovery for LT inhibitors to prevent inflammatory diseases. A newly important detrimental role for LTs in comorbidities associated with metabolic stress has emerged in the last few years and managing LT production and/or actions could represent an exciting new strategy to prevent or treat inflammatory diseases associated with metabolic disorders. This review is intended to shed light on the synthesis and actions of leukotrienes, the most common drugs used in clinical trials, and discuss the therapeutic potential of preventing LT function in obesity, diabetes, and hyperlipidemia.

Eicosanoid biosynthesis in marine mammals

After 300 million years of evolution, the first land-living mammals reentered the marine environment some 50 million years ago. The driving forces for this dramatic lifestyle change are still a matter of discussion but the struggle for food resources and the opportunity to escape predators probably contributed. Reentering the oceans requires metabolic adaption putting evolutionary pressure on a number of genes. To explore whether eicosanoid signaling has been part of this adaptive response, we first explored whether the genomes of marine mammals involve functional genes encoding for key enzymes of eicosanoid biosynthesis. Cyclooxygenase (COX) and lipoxygenase (ALOX) genes are present in the genome of all marine mammals tested. Interestingly, ALOX12B, which has been implicated in skin development of land-living mammals, is lacking in whales and dolphins and genes encoding for its sister enzyme (ALOXE3) involve premature stop codons and/or frameshifting point mutations, which interrupt the open reading frames. ALOX15 orthologs have been detected in all marine mammals, and the recombinant enzymes exhibit similar catalytic properties as those of land-living species. All marine mammals express arachidonic acid 12-lipoxygenating ALOX15 orthologs, and these data are consistent with the Evolutionary Hypothesis of ALOX15 specificity. These enzymes exhibit membrane oxygenase activity and introduction of big amino acids at the triad positions altered the reaction specificity in favor of arachidonic acid 15-lipoxygenation. Thus, the ALOX15 orthologs of marine mammals follow the Triad concept explaining their catalytic specificity.

Delayed extensive brain edema caused by the growth of a giant basilar apex aneurysm treated with basilar artery obliteration: a case report

Background

Partially thrombosed giant aneurysms at the basilar apex (BA) artery are challenging lesions with a poor prognosis if left untreated. Here we describe a rare case of extensive brain edema after growth of a surgically treated and thrombosed giant basilar apex aneurysm.

Case presentation

We performed a proximal surgical basilar artery occlusion on a 64-year-old female with a partially thrombosed giant BA aneurysm. MRI showed no ischemic lesions but showed marked edema adjacent to the aneurysm. She had a good recovery, but 3 months after surgical occlusion, her gait deteriorated together with urinary incontinence and worsening right hemiparesis. MRI showed that the aneurysm had grown and developed intramural hemorrhage, which caused extensive brain edema and obstructive hydrocephalus. She was treated by a ventriculoperitoneal shunt placement. Follow-up MRI showed progressive brain edema resolution, complete thrombosis of the lumen and shrinkage of the aneurysm. At 5 years follow-up the patient had an excellent functional outcome.

Conclusions

Delayed growth of a surgically treated and thrombosed giant aneurysm from wall dissection demonstrates that discontinuity with the initial parent artery does not always prevent progressive enlargement. The development of transmural vascular connections between the intraluminal thrombus and adventitial neovascularization by the vasa vasorum on the apex of the BA seems to be a key event in delayed aneurysm growth. Extensive brain edema might translate an inflammatory edematous reaction to an abrupt enlargement of the aneurysm.

Pathogenesis of atherosclerosis in the tunica intima, media, and adventitia of coronary arteries: An updated review

Atherosclerosis is a chronic inflammatory disease of arteries and it affects the structure and function of all three layers of the coronary artery wall. Current theories suggest that the dysfunction of endothelial cells is one of the initial steps in the development of atherosclerosis. The view that the tunica intima normally consists of a single layer of endothelial cells attached to the subendothelial layer and internal elastic membrane has been questioned in recent years. The structure of intima changes with age and it becomes multilayered due to migration of smooth muscle cells from the media to intima. At this stage, the migration and proliferation of smooth muscle cells do not cause pathological changes in the intima. The multilayering of intima is classically considered to be an important stage in the development of atherosclerosis, but in fact atherosclerotic plaques develop only focally due to the interplay of various processes that involve the resident and invading inflammatory cells. The tunica media consists of multiple layers of smooth muscle cells that produce the extracellular matrix, and this layer normally does not contain microvessels. During the development of atherosclerosis, the microvessels from the tunica adventitia or from the lumen may penetrate thickened media to provide nutrition and oxygenation. According to some theories, the endothelial dysfunction of these nutritive vessels may significantly contribute to the atherosclerosis of coronary arteries. The adventitia contains fibroblasts, progenitor cells, immune cells, microvessels, and adrenergic nerves. The degree of inflammatory cell infiltration into the adventitia, which can lead to the formation of tertiary lymphoid organs, correlates with the severity of atherosclerotic plaques. Coronary arteries are surrounded by perivascular adipose tissue that also participates in the atherosclerotic process.

Functional Characterization of Knock-In Mice Expressing a 12/15-Lipoxygenating Alox5 Mutant Instead of the 5-Lipoxygenating Wild-Type Enzyme

Aims: Most mammalian genomes involve several genes encoding for functionally distinct arachidonate lipoxygenase (ALOX isoforms). Proinflammatory leukotrienes are formed via the ALOX5 pathway, but 12/15-lipoxygenating ALOX isoforms have been implicated in the biosynthesis of pro-resolving mediators. In vitro mutagenesis of the triad determinants abolished the leukotriene synthesizing activity of ALOX5, but the biological consequences of these alterations have not been studied. To fill this gap, we created Alox5 knock-in mice, which express the 12/15-lipoxygenating Phe359Trp + Ala424Ile + Asn425Met Alox5 triple mutant and characterized its phenotypic alterations. Results: The mouse Alox5 triple mutant functions as arachidonic acid 15-lipoxygenating enzyme, which also forms 12S-hydroxy and 8S-hydroxy arachidonic acid. In contrast to the wild-type enzyme, the triple mutant effectively oxygenates linoleic acid to 13S-hydroxy linoleic acid (13S-HODE), which functions as activating ligand of the type-2 nuclear receptor peroxisome proliferator-activated receptor gamma (PPARγ). Knock-in mice expressing the mutant enzyme are viable, fertile, and develop normally. The mice cannot synthesize proinflammatory leukotrienes but show significantly attenuated plasma levels of lipolytic endocannabinoids. When aging, the animals gained significantly more body weight, which may be related to the fivefold higher levels of 13-HODE in the adipose tissue. Innovation: These data indicate for the first time that in vivo mutagenesis of the triad determinants of mouse Alox5 abolished the biosynthetic capacity of the enzyme for proinflammatory leukotrienes and altered the catalytic properties of the protein favoring the formation of 13-HODE. Conclusion:In vivo triple mutation of the mouse Alox5 gene impacts the body weight homeostasis of aging mice via augmented formation of the activating PPARγ ligand 13-HODE.

The lipoxygenase pathway of Tupaia belangeri representing Scandentia. Genomic multiplicity and functional characterization of the ALOX15 orthologs in the tree shrew

The tree shrew (Tupaia belangeri) is a rat-sized mammal, which is more closely related to humans than mice and rats. However, the use of tree shrew to explore the patho-mechanisms of human inflammatory disorders has been limited since nothing is known about eicosanoid metabolism in this mammalian species. Eicosanoids are important lipid mediators exhibiting pro- and anti-inflammatory activities, which are biosynthesized via lipoxygenase and cyclooxygenase pathways. When we searched the tree shrew genome for the presence of cyclooxygenase and lipoxygenase isoforms we found copies of functional COX1, COX2 and LOX genes. Interestingly, we identified four copies of ALOX15 genes, which encode for four structurally distinct ALOX15 orthologs (tupALOX15a-d). To explore the catalytic properties of these enzymes we expressed tupALOX15a and tupALOX15c as catalytically active proteins and characterized their enzymatic properties. As predicted by the Evolutionary Hypothesis of ALOX15 specificity we found that the two enzymes converted arachidonic acid predominantly to 12S-HETE and they also exhibited membrane oxygenase activities. However, their reaction kinetic properties (K_M for arachidonic acid and oxygen, T- and pH-dependence) and their substrate specificities were remarkably different. In contrast to mice and humans, tree shrew ALOX15 isoforms are highly expressed in the brain suggesting a role of these enzymes in cerebral function. The genomic multiplicity and the tissue expression patterns of tree shrew ALOX15 isoforms need to be considered when the results of in vivo inflammation studies obtained in this animal are translated into the human situation.

Inflammation promotes progression of thrombi in intracranial thrombotic aneurysms

Advances in the understanding of the pathogenesis of arteriosclerosis, abdominal aorta aneurysms and dissections, and carotid artery plaques have focused on chronic inflammation. In this study, we report that inflammatory changes of thrombi contribute to the enlargement and growth of giant intracranial thrombotic aneurysms. Surgical and postmortem samples were collected from 12 cases of large or giant intracranial thrombotic aneurysms diagnosed via pathological investigations. Degeneration of the aneurysmal wall and the infiltration of inflammatory cells in the thrombi were assessed. The number of blood cells and immunohistochemical stain-positive cells was enumerated, and the inflammation and neovascularization in the thrombi were assessed. In all cases, the appearance of inflammatory cells (CD68⁺ cells, CD206⁺ cells, lymphocytes, and neutrophils) was apparent in the thrombi. The number of CD34⁺ cells was moderately correlated with the number of CD68⁺ cells, and CD34⁺ cells significantly and strongly correlated with the number of CD206⁺ cells. Based on the number of neutrophils per CD68⁺ cells, we classified the cases into 2 groups: a macrophage inflammation-dominant group and a neutrophilic inflammation-dominant group. The neutrophilic inflammation-dominant group had significantly more cases with previous treatments and neurological symptoms due to mass effect than the macrophage inflammation-dominant group. Chronic inflammation due to macrophages in thrombi is a fundamental mechanism in the enlargement of an intracranial thrombotic aneurysm, and neutrophilic inflammation can accelerate this process. Microvascularization in thrombi is linked to inflammation and might promote thickening of the intima and repeated intimal microbleeds.

Dysregulation of microRNAs and target genes networks in human abdominal aortic aneurysm tissues

BACKGROUND

Abdominal aortic aneurysm (AAA) is a pathological enlargement of infrarenal aorta close to the aortic bifurcation, and it is an important cause of mortality in the elderly. Therefore, the biomarker identification for early diagnosis is of great interest for clinical benefit. It is known that microRNAs (miRNAs) have important roles via target genes regulation in many diseases. This study aimed to identify miRNAs and their target genes involved in the pathogenesis of AAA.

METHODS

Tissue samples were obtained from patients who underwent AAA surgery and from organ donors (control group). Quantitative PCR Array was applied to assess 84 genes and 384 miRNAs aiming to identify differentially expressed targets (AAA n = 6, control n = 6), followed by validation in a new cohort (AAA n = 18, control n = 6) by regular qPCR. The functional interaction between validated miRNAs and target genes was performed by the Ingenuity Pathway Analysis (IPA) software.

RESULTS

The screening cohort assessed by PCR array identified 10 genes and 59 miRNAs differentially expressed (≥2-fold change, p<0.05). Among these, IPA identified 5 genes and 9 miRNAs with paired interaction. ALOX5, PTGIS, CX3CL1 genes, and miR-193a-3p, 125b-5p, 150-5p maintained a statistical significance in the validation cohort. IPA analysis based on the validated genes and miRNAs revealed that eicosanoid and metalloproteinase/TIMP synthesis are potentially involved in AAA.

CONCLUSION

Paired interactions of differentially expressed ALOX5, PTGIS, CX3CL1 genes, and miR-193b-3p, 125b-5p, 150-5p revealed a potentially significant role of the eicosanoid synthesis and metalloproteinase/TIMP pathways in the AAA pathogenesis.

Montelukast Prevents Mice Against Acetaminophen-Induced Liver Injury

Acetaminophen (APAP) is a widely used over-the-counter antipyretic and analgesic drug. Overdose of APAP is the leading cause of hospital admission for acute liver failure. Montelukast is an antagonist of cysteinyl leukotriene receptor 1 (Cysltr1), which protects from inflammation and oxidative stress. However, the function of montelukast in APAP-induced hepatotoxicity remains unknown. In this study, we examined whether pharmacological inhibition of Cystlr1 could protect mice against APAP-induced hepatic damage. We found that APAP treatment upregulated messenger RNA and protein levels of Cysltr1 both in vitro and in vivo. Pharmacological inhibition of Cysltr1 by montelukast ameliorated APAP-induced acute liver failure. The hepatoprotective effect of montelukast was associated with upregulation of hepatic glutathione/glutathione disulfide level, reduction in c-Jun-NH2-terminal kinase activation and oxidative stress. In mouse primary hepatocytes, inhibition of Cysltr1 by montelukast ameliorated the expression of inflammatory-related genes and APAP-induced cytotoxicity. We conclude that montelukast may be used to treat APAP-induced acute hepatic injury.

Urotensin II promotes secretion of LTB4 through 5-lipoxygenase via the UT-ROS-Akt pathway in RAW264.7 macrophages

INTRODUCTION

Urotensin II (UII) is an important vasoactive peptide involved in the pathogenesis of atherosclerosis. Monocytes/macrophages play important roles in every step of atherosclerosis. Although UII has a chemoattractant effect on monocytes, it is unclear whether UII regulates inflammatory responses in macrophages. The present study sought to explore whether UII can promote leukotriene B₄ (LTB₄) production by macrophages.

MATERIAL AND METHODS

The mRNA expression level of LTB₄ and 5-lipoxygenase were determined by real-time polymerase chain reaction. The protein level of LTB₄ and 5-lipoxygenase expression was assayed by enzyme-linked immunosorbent assay and Western blot, respectively. Western blot analysis was also employed to determine the phosphorylated forms of Akt. Reactive oxygen species (ROS) level was detected by the fluorescent probe 2',7'-dichlorofluorescin diacetate and fluorescence intensity was measured with a multiwell fluorescence plate reader.

RESULTS

Urotensin II promoted LTB₄ release and increased 5-lipoxygenase expression in a concentration- and time-dependent manner in RAW264.7 cells. Leukotriene B4 production and 5-lipoxygenase expression were decreased by blocking the UII receptor (UT) with urantide, eliminating ROS with N-acetylcysteine and diphenyliodonium, and inhibiting Akt phosphorylation with LY294002. UII significantly elevated ROS production, whereas urantide, N-acetylcysteine and diphenyliodonium substantially attenuated this effect. UII also enhanced Akt phosphorylation significantly, and this effect was potently inhibited by urantide, N-acetylcysteine, diphenyliodonium and LY294002.

CONCLUSIONS

Urotensin II may promote 5-lipoxygenase expression and LTB₄ release in RAW264.7 macrophages via UT-ROS-Akt pathways. These results indicate that UII may participate in macrophage activation and suggest a potential new mechanism underlying atherosclerosis.

Montelukast, a Cysteinyl Leukotriene Receptor 1 Antagonist, Induces M2 Macrophage Polarization and Inhibits Murine Aortic Aneurysm Formation

Background

The pathogenesis of abdominal aortic aneurysm (AAA) is characterized by atherosclerosis with chronic inflammation in the aortic wall. Montelukast is a selective cys-LT 1 receptor antagonist that can suppress atherosclerotic diseases. We evaluated the in vitro properties of montelukast and its in vivo activities in an angiotensin II–infused apolipoprotein E–deficient (apoE^−/−) AAA mouse model.

Methods

The mouse monocyte/macrophage cell line J774A.1 was used in vitro. M1 macrophages were treated with montelukast, and gene expressions of inflammatory cytokines were measured. Macrophages were cultured with montelukast, then gene expressions of arginase-1 and IL (interleukin)-10 were assessed by quantitative polymerase chain reaction, arginase-1 was measured by fluorescence-activated cell sorting, and IL-10 concentration was analyzed by enzyme-linked immunosorbent assay. In vivo, one group (Mont, n=7) received oral montelukast (10 mg/kg/day) for 28 days, and the other group (Saline, n=7) was given normal Saline as a control for the same period. Aortic diameters, activities of matrix metalloproteinases (MMPs), cytokine concentrations, and the number of M2 macrophages were analyzed.

Results

Relative to control, montelukast significantly suppressed gene expressions of MMP-2, MMP-9, and IL-1β, induced gene expressions of arginase-1 and IL-10, enhanced the expression of the arginase-1 cell surface protein, and increased the protein concentration of IL-10. In vivo, montelukast significantly decreased aortic expansion (Saline vs Mont; 2.44 ± 0.15 mm vs 1.59 ± 0.20 mm, P<.01), reduced MMP-2 activity (Saline vs Mont; 1240 μM vs 755 μM, P<.05), and induced infiltration of M2 macrophages (Saline vs Mont; 7.51 % vs 14.7 %, P<.05).

Conclusion

Montelukast induces M2 macrophage polarization and prevents AAA formation in apoE^−/− mice.

Identification of key genes and pathways contributing to artery tertiary lymphoid organ development in advanced mouse atherosclerosis

Atherosclerosis is a leading cause of mortality worldwide. Artery tertiary lymphoid organ (ATLO) neogenesis is affected by abdominal aorta atherosclerosis, which may lead to an immune response. The present study obtained microarray data to investigate the gene expression differences underlying the potential pathogenesis of atherosclerosis and to elucidate the mechanisms underlying ATLO development. Microarray studies of the aorta, plaques, adventitia, blood, spleen, renal lymph nodes and ATLO were downloaded from the Gene Expression Omnibus database. Differentially expressed genes (DEGs) were identified in aorta clusters and ATLO clusters. Kyoto Encyclopedia of Genes and Genomes enrichment and Gene Ontology (GO) analyses were conducted to predict the biological functions of DEGs. The results demonstrated that interleukin 7 receptor (Il7r), C‑X‑C motif chemokine ligand (Cxcl)16, Cxcl13, Cxcl12, C‑C motif chemokine receptor 2, C‑C motif chemokine ligand (Ccl)8, Ccl5 and Ccl12 may function through pathways associated with 'cytokine‑cytokine receptor interaction' and 'chemokine signaling pathway' in ATLO. Gene expression alterations were validated by reverse transcription‑quantitative polymerase chain reaction. Il7r appeared to be the central gene involved in these events, and chemokines and/or chemokine receptors were visualized by GO enrichment. A protein‑protein interaction network was constructed, which suggested that Il7r had a core function in all clusters. Taken together, the results indicated that Il7r upregulation may serve an important role in ATLO development via 'cytokine‑cytokine receptor interaction' and 'chemokine signaling pathway'. This may provide novel perspectives for understanding ATLO development and the regulation of the immune response in atherosclerosis.

ApoE attenuates unresolvable inflammation by complex formation with activated C1q

ApoE has been implicated in Alzheimer´s disease, atherosclerosis, and other unresolvable inflammatory conditions but a common mechanism of action remains elusive. We found in ApoE-deficient mice that oxidized lipids activated the classical complement cascade (CCC) resulting in leukocyte infiltration of the choroid plexus (ChP). All human ApoE isoforms attenuated CCC activity via high-affinity binding to the activated CCC-initiating C1q protein (K_D~140-580 pM) in vitro; and C1q-ApoE complexes emerged as markers for ongoing complement activity of diseased ChPs, Aβ plaques, and atherosclerosis in vivo. C1q-ApoE complexes in human ChPs, Aβ plaques, and arteries correlated with cognitive decline and atherosclerosis, respectively. Treatment with siRNA against C5 which is formed by all complement pathways, attenuated murine ChP inflammation, Aβ-associated microglia accumulation, and atherosclerosis. Thus, ApoE is a direct checkpoint inhibitor of unresolvable inflammation and reducing C5 attenuates disease burden.

Arachidonic Acid Metabolites in Cardiovascular and Metabolic Diseases

Lipid and immune pathways are crucial in the pathophysiology of metabolic and cardiovascular disease. Arachidonic acid (AA) and its derivatives link nutrient metabolism to immunity and inflammation, thus holding a key role in the emergence and progression of frequent diseases such as obesity, diabetes, non-alcoholic fatty liver disease, and cardiovascular disease. We herein present a synopsis of AA metabolism in human health, tissue homeostasis, and immunity, and explore the role of the AA metabolome in diverse pathophysiological conditions and diseases.

Targeting cysteinyl-leukotrienes in abdominal aortic aneurysm

Abdominal aortic aneurysm (AAA) is an asymptomatic dilatation of the vessel wall exceeding the normal vessel diameter by 50%, accompanied by intramural thrombus formation. Since the aneurysm can rupture, AAA is a life-threatening vascular disease, which may be amenable to surgical repair. At present, no pharmacological therapy for AAA is available. The 5-lipoxygenase (5-LOX) pathway of arachidonic acid metabolism leads to biosynthesis of leukotrienes (LTs), potent lipid mediators with pro-inflammatory biological actions. Among the LTs, cysteinyl-leukotrienes (cys-LT) are well-recognized signaling molecules in human asthma and allergic rhinitis. However, the effects of these molecules in cardiovascular diseases have only recently been explored. Drugs antagonizing the CysLT1 receptor, termed lukasts and typified by montelukast, are established therapeutics for clinical management of asthma. Lukasts are safe, well-tolerated drugs that can be administered during long time periods. Here we describe recent data indicating that montelukast may be used for prevention and treatment of AAA, thus representing a promising pharmacological tool for a deadly vascular disease with significant socio-economic impact.

Leukotriene biosynthetic enzymes as therapeutic targets

Leukotrienes are powerful immune-regulating lipid mediators with established pathogenic roles in inflammatory allergic diseases of the respiratory tract - in particular, asthma and hay fever. More recent work indicates that these lipids also contribute to low-grade inflammation, a hallmark of cardiovascular, neurodegenerative, and metabolic diseases as well as cancer. Biosynthesis of leukotrienes involves oxidative metabolism of arachidonic acid and proceeds via a set of soluble and membrane enzymes that are primarily expressed by cells of myeloid origin. In activated immune cells, these enzymes assemble at the endoplasmic and perinuclear membrane, constituting a biosynthetic complex. This Review describes recent advances in our understanding of the components of the leukotriene-synthesizing enzyme machinery, emerging opportunities for pharmacological intervention, and the development of new medicines exploiting both antiinflammatory and pro-resolving mechanisms.

Participation of Arachidonic Acid Metabolism in the Aortic Aneurysm Formation in Patients with Marfan Syndrome

Marfan syndrome (MFS) is a pleiotropic genetic disease involving the cardiovascular system where a fibrillin-1 mutation is present. This mutation is associated with accelerated activation of transforming growth factor β (TGFβ1) which contributes to the formation of aneurysms in the root of the aorta. There is an imbalance in the synthesis of thromboxane A₂ (TXA₂) and prostacyclin, that is a consequence of a differential protein expression of the isoforms of cyclooxygenases (COXs), suggesting an alteration of arachidonic acid (AA) metabolism. The aim of this study was to analyze the participation of AA metabolism associated with inflammatory factors in the dilation and dissection of the aortic aneurysm in patients with MFS. A decrease in AA (p = 0.02), an increase in oleic acid (OA), TGFβ1, tumor necrosis factor alpha (TNFα), prostaglandin E₂ (PGE₂) (p < 0.05), and COXs activity (p = 0.002) was found. The expressions of phospholipase A₂ (PLA₂), cytochrome P450 (CYP450 4A), 5-lipoxygenase (5-LOX), COX2 and TXA2R (p < 0.05) showed a significant increase in the aortic aneurysm of patients with MFS compared to control subjects. COX1, 6-keto-prostaglandin 1 alpha (6-keto-PG_1α) and 8-isoprostane did not show significant changes. Histological examination of the aortas showed an increase of cystic necrosis, elastic fibers and collagen in MFS. The results suggest that there are inflammatory factors coupled to genetic factors that predispose to aortic endothelial dysfunction in the aortic tissue of patients with MFS. There is a decrease in the percentage of AA, associated with an increase of PLA₂, COX2/TXA2R, CYP450 4A, and 5-LOX which leads to a greater synthesis of PGE₂ than of 6-keto-PGF_1α, thus contributing to the formation of the aortic aneurysm. The evident loss of the homeostasis in these mechanisms confirms that there is a participation of the AA pathway in the aneurysm progression in MFS.

Cysteinyl leukotriene receptor 1 antagonism prevents experimental abdominal aortic aneurysm

Cysteinyl-leukotrienes (cys-LTs) are lipid mediators involved in human inflammatory diseases, in particular asthma. We have previously identified cys-LTs in tissue specimens of human abdominal aortic aneurysm (AAA) and linked these mediators to increased metalloproteinase activity. Here we show in vivo that antagonism of the CysLT1 receptor by montelukast, an established antiasthma drug, protects against aneurysm in three mouse models of AAA at doses comparable to human medical practice. Together, these data support the role of cys-LTs in AAA and indicate a new potential therapeutic approach for treatment of this clinically silent and highly lethal disease.

Cysteinyl-leukotrienes (cys-LTs) are 5-lipoxygenase-derived lipid mediators involved in the pathogenesis and progression of inflammatory disorders, in particular asthma. We have previously found evidence linking these mediators to increased levels of proteolytic enzymes in tissue specimens of human abdominal aortic aneurysm (AAA). Here we show that antagonism of the CysLT1 receptor by montelukast, an established antiasthma drug, protects against a strong aorta dilatation (>50% increase = aneurysm) in a mouse model of CaCl₂-induced AAA at a dose comparable to human medical practice. Analysis of tissue extracts revealed that montelukast reduces the levels of matrix metalloproteinase-9 (MMP-9) and macrophage inflammatory protein-1α (MIP-1α) in the aortic wall. Furthermore, aneurysm progression was specifically mediated through CysLT1 signaling since a selective CysLT2 antagonist was without effect. A significantly reduced vessel dilatation is also observed when treatment with montelukast is started days after aneurysm induction, suggesting that the drug not only prevents but also stops and possibly reverts an already ongoing degenerative process. Moreover, montelukast reduced the incidence of aortic rupture and attenuated the AAA development in two additional independent models, i.e., angiotensin II- and porcine pancreatic elastase-induced AAA, respectively. Our results indicate that cys-LTs are involved in the pathogenesis of AAA and that antagonism of the CysLT1 receptor is a promising strategy for preventive and therapeutic treatment of this clinically silent and highly lethal disease.

Adventitial tertiary lymphoid organ classification in human atherosclerosis

BACKGROUND

Atherosclerosis is a chronic inflammatory disease of the arterial wall. Adjacent to lamina intima lesion progression, a cellular compound develops in the lamina adventitia, defined as tertiary lymphoid organs (TLO) in mice. But in human system, it remains unknown whether these adventitial cellular accumulations represent these highly organized immunological structures.

PATIENTS AND METHODS

In this study, we investigated whether the adventitial cellular compounds represent TLOs in 72 human coronary artery samples by immunoenzyme staining.

RESULTS

The study showed that the adventitial cellular compound partly represented TLOs in human coronary arteries affected by atherogenesis in patients suffering from ischemic heart disease (56%) or a fatal myocardial infarction (100%), but not dilated cardiomyopathy. In addition, we established a classification for human TLOs, stage I-III, and showed that all stages were present in diseased coronary arteries. The stage of TLOs highly correlated with lesion size as well as plaque instability and rupture, and all patients with a myocardial infarction had stage III. Additionally, there were cellular infiltration and destruction of the lamina media, which were restricted to TLOs next to ruptured plaques in patients with a fatal myocardial infarction.

CONCLUSIONS

TLOs are present in patients with a coronary artery disease and highly correlated with lesion size, plaque instability, and rupture. Further studies are needed to investigate whether TLOs might be a specific diagnostic and drug target to modify plaque instability/rupture.

Role of the Cysteinyl Leukotrienes in the Pathogenesis and Progression of Cardiovascular Diseases

Cysteinyl leukotrienes (CysLTs) are potent lipid inflammatory mediators synthesized from arachidonic acid, through the 5-lipoxygenase (5-LO) pathway. Owing to their properties, CysLTs play a crucial role in the pathogenesis of inflammation; therefore, CysLT modifiers as synthesis inhibitors or receptor antagonists, central in asthma management, may become a potential target for the treatment of other inflammatory diseases such as the cardiovascular disorders. 5-LO pathway activation and increased expression of its mediators and receptors are found in cardiovascular diseases. Moreover, the cardioprotective effects observed by using CysLT modifiers are promising and contribute to elucidate the link between CysLTs and cardiovascular disease. The aim of this review is to summarize the state of present research about the role of the CysLTs in the pathogenesis and progression of atherosclerosis and myocardial infarction.

Boosting Inflammation Resolution in Atherosclerosis: The Next Frontier for Therapy

Defective inflammation resolution is the underlying cause of prevalent chronic inflammatory diseases, such as arthritis, asthma, cancer, and neurodegenerative and cardiovascular diseases. Inflammation resolution is governed by several endogenous factors, including fatty acid-derived specialized proresolving mediators and proteins, such as annexin A1. Specifically, specialized proresolving mediators comprise a family of mediators that include arachidonic acid-derived lipoxins, omega-3 fatty acid eicosapentaenoic acid-derived resolvins, docosahexaenoic acid-derived resolvins, protectins, and maresins. Emerging evidence indicates that imbalances between specialized proresolving mediators and proinflammatory mediators are associated with several prevalent human diseases, including atherosclerosis. Mechanisms that drive this imbalance remain largely unknown and will be discussed in this review. Furthermore, the concept of dysregulated inflammation resolution in atherosclerosis has been known for several decades. Recently, there has been an explosion of new work with regard to the therapeutic application of proresolving ligands in experimental atherosclerosis. Therefore, this review will highlight recent advances in our understanding of how inflammation resolution may become defective in atherosclerosis and the potential for proresolving therapeutics in atherosclerosis. Last, we offer insight for future implications of the field.

Lipid Mediators in Inflammation

Lipids are potent signaling molecules that regulate a multitude of cellular responses, including cell growth and death and inflammation/infection, via receptor-mediated pathways. Derived from polyunsaturated fatty acids (PUFAs), such as arachidonic acid (AA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA), each lipid displays unique properties, thus making their role in inflammation distinct from that of other lipids derived from the same PUFA. This diversity arises from their synthesis, which occurs via discrete enzymatic pathways and because they elicit responses via different receptors. This review will collate the bioactive lipid research to date and summarize the major pathways involved in their biosynthesis and role in inflammation. Specifically, lipids derived from AA (prostanoids, leukotrienes, 5-oxo-6,8,11,14-eicosatetraenoic acid, lipoxins, and epoxyeicosatrienoic acids), EPA (E-series resolvins), and DHA (D-series resolvins, protectins, and maresins) will be discussed herein.

Type-2 innate lymphoid cells control the development of atherosclerosis in mice

Type-2 innate lymphoid cells (ILC2) are a prominent source of type II cytokines and are found constitutively at mucosal surfaces and in visceral adipose tissue. Despite their role in limiting obesity, how ILC2s respond to high fat feeding is poorly understood, and their direct influence on the development of atherosclerosis has not been explored. Here, we show that ILC2 are present in para-aortic adipose tissue and lymph nodes and display an inflammatory-like phenotype atypical of adipose resident ILC2. High fat feeding alters both the number of ILC2 and their type II cytokine production. Selective genetic ablation of ILC2 in Ldlr^−/− mice accelerates the development of atherosclerosis, which is prevented by reconstitution with wild type but not Il5^−/− or Il13^−/− ILC2. We conclude that ILC2 represent a major innate cell source of IL-5 and IL-13 required for mounting atheroprotective immunity, which can be altered by high fat diet.

Type-2 innate lymphoid cells (ILC2) affect adipose tissue metabolism and function. Here the authors show that the ILC2 are present in para-aortic adipose tissue and represent a major source of IL-5 and IL-13 required for mounting atheroprotective immunity, which can be altered by high fat diet.

The leukotriene receptor antagonist montelukast and its possible role in the cardiovascular field

BACKGROUND

Cysteinyl leukotrienes (LTC4, LTD4, and LTE4) are pro-inflammatory mediators of the 5-lipooxygenase (5-LO) pathway, that play an important role in bronchoconstriction, but can also enhance endothelial cell permeability and myocardial contractility, and are involved in many other inflammatory conditions. In the late 1990s, leukotriene receptor antagonists (LTRAs) were introduced in therapy for asthma and later on, approved for the relief of the symptoms of allergic rhinitis, chronic obstructive pulmonary disease, and urticaria. In addition, it has been shown that LTRAs may have a potential role in preventing atherosclerosis progression.

PURPOSE

The aims of this short review are to delineate the potential cardiovascular protective role of a LTRA, montelukast, beyond its traditional use, and to foster the design of appropriate clinical trials to test this hypothesis.

RESULTS AND CONCLUSIONS

What it is known about leukotriene receptor antagonists? •Leukotriene receptor antagonist, such as montelukast and zafirlukast, is used in asthma, COPD, and allergic rhinitis. • Montelukast is the most prescribed CysLT₁ antagonist used in asthmatic patients. • Different in vivo animal studies have shown that leukotriene receptor antagonists can prevent the atherosclerosis progression, and have a protective role after cerebral ischemia. What we still need to know? • Today, there is a need for conducting clinical trials to assess the role of montelukast in reducing cardiovascular risk and to further understand the mechanism of action behind this effect.

Adventitial lymphatic capillary expansion impacts on plaque T cell accumulation in atherosclerosis

During plaque progression, inflammatory cells progressively accumulate in the adventitia, paralleled by an increased presence of leaky vasa vasorum. We here show that next to vasa vasorum, also the adventitial lymphatic capillary bed is expanding during plaque development in humans and mouse models of atherosclerosis. Furthermore, we investigated the role of lymphatics in atherosclerosis progression. Dissection of plaque draining lymph node and lymphatic vessel in atherosclerotic ApoE^-/- mice aggravated plaque formation, which was accompanied by increased intimal and adventitial CD3⁺ T cell numbers. Likewise, inhibition of VEGF-C/D dependent lymphangiogenesis by AAV aided gene transfer of hVEGFR3-Ig fusion protein resulted in CD3⁺ T cell enrichment in plaque intima and adventitia. hVEGFR3-Ig gene transfer did not compromise adventitial lymphatic density, pointing to VEGF-C/D independent lymphangiogenesis. We were able to identify the CXCL12/CXCR4 axis, which has previously been shown to indirectly activate VEGFR3, as a likely pathway, in that its focal silencing attenuated lymphangiogenesis and augmented T cell presence. Taken together, our study not only shows profound, partly CXCL12/CXCR4 mediated, expansion of lymph capillaries in the adventitia of atherosclerotic plaque in humans and mice, but also is the first to attribute an important role of lymphatics in plaque T cell accumulation and development.

Cross-Talk between Cancer Cells and the Tumour Microenvironment: The Role of the 5-Lipoxygenase Pathway

5-lipoxygenase is an enzyme responsible for the synthesis of a range of bioactive lipids signalling molecules known collectively as eicosanoids. 5-lipoxygenase metabolites such as 5-hydroxyeicosatetraenoic acid (5-HETE) and a number of leukotrienes are mostly derived from arachidonic acid and have been shown to be lipid mediators of inflammation in different pathological states including cancer. Upregulated 5-lipoxygenase expression and metabolite production is found in a number of cancer types and has been shown to be associated with increased tumorigenesis. 5-lipoxygenase activity is present in a number of diverse cell types of the immune system and connective tissue. In this review, we discuss potential routes through which cancer cells may utilise the 5-lipoxygenase pathway to interact with the tumour microenvironment during the development and progression of a tumour. Furthermore, immune-derived 5-lipoxygenase signalling can drive both pro- and anti-tumour effects depending on the immune cell subtype and an overview of evidence for these opposing effects is presented.

Genetic and Epigenetic Regulation of Aortic Aneurysms

Aneurysms are characterized by structural deterioration of the vascular wall leading to progressive dilatation and, potentially, rupture of the aorta. While aortic aneurysms often remain clinically silent, the morbidity and mortality associated with aneurysm expansion and rupture are considerable. Over 13,000 deaths annually in the United States are attributable to aortic aneurysm rupture with less than 1 in 3 persons with aortic aneurysm rupture surviving to surgical intervention. Environmental and epidemiologic risk factors including smoking, male gender, hypertension, older age, dyslipidemia, atherosclerosis, and family history are highly associated with abdominal aortic aneurysms, while heritable genetic mutations are commonly associated with aneurysms of the thoracic aorta. Similar to other forms of cardiovascular disease, family history, genetic variation, and heritable mutations modify the risk of aortic aneurysm formation and provide mechanistic insight into the pathogenesis of human aortic aneurysms. This review will examine the relationship between heritable genetic and epigenetic influences on thoracic and abdominal aortic aneurysm formation and rupture.

Artery Tertiary Lymphoid Organs: Powerhouses of Atherosclerosis Immunity

Artery tertiary lymphoid organs (ATLOs) are atherosclerosis-associated lymphoid aggregates with varying degrees of complexity ranging from small T/B-cell clusters to well-structured lymph node-like though unencapsulated lymphoid tissues. ATLOs arise in the connective tissue that surrounds diseased arteries, i.e., the adventitia. ATLOs have been identified in aged atherosclerosis-prone hyperlipidemic apolipoprotein E-deficient (ApoE-/-) mice: they are organized into distinct immune cell compartments, including separate T-cell areas, activated B-cell follicles, and plasma cell niches. Analyses of ATLO immune cell subsets indicate antigen-specific T- and B-cell immune reactions within the atherosclerotic arterial wall adventitia. Moreover, ATLOs harbor innate immune cells, including a large component of inflammatory macrophages, B-1 cells, and an aberrant set of antigen-presenting cells. There is marked neoangiogenesis, irregular lymphangiogenesis, neoformation of high endothelial venules, and de novo synthesis of lymph node-like conduits. Molecular mechanisms of ATLO formation remain to be identified though media vascular smooth muscle cells may adopt features of lymphoid tissue organizer-like cells by expressing lymphorganogenic chemokines, i.e., CXCL13 and CCL21. Although these data are consistent with the view that ATLOs participate in primary T- and B-cell responses against elusive atherosclerosis-specific autoantigens, their specific protective or disease-promoting roles remain to be identified. In this review, we discuss what is currently known about ATLOs and their potential impact on atherosclerosis and make attempts to define challenges ahead.