Differential leukotriene constrictor responses in human atherosclerotic coronary arteries

Disposition of orally administered atuliflapon, a novel 5-lipoxygenase-activating protein inhibitor in healthy participants

In this study, the mass balance, pharmacokinetics (PK) and metabolism of atuliflapon, a novel 5-lipoxygenase-activating protein inhibitor, were investigated in healthy male subjects. A single oral dose of 200 mg [14C]atuliflapon suspension was administered to six healthy male subjects. Mass balance, PK and metabolite profiles of atuliflapon were analyzed using radioactivity monitoring and liquid chromatography with mass spectrometry analysis. The safety of atuliflapon was assessed during the study. Atuliflapon was rapidly absorbed with a median tmax of 1.5 h, followed by a biphasic decline in plasma exposure rendering a terminal half-life of ~20 h. Unchanged atuliflapon was the predominant radioactive component in plasma, accounting for 40.1% of the total drug-related exposure (DRE), while a direct N-glucuronide was the only metabolite exceeding 10% of DRE, accounting for 20.9%. Renal excretion of intact atuliflapon accounted for <1% of the administered dose. In total 85.2% of administered radioactivity was recovered over 312 h with 79.3% and 5.9% in feces and urine, respectively. Parent atuliflapon contributed to approximately 40% of the recovered dose in excreta, while metabolites resulting from phase 1 oxidative pathways accounted for more than 30% of the excreted dose. Overall, a single oral dose of 200 mg [14C]atuliflapon suspension was well tolerated in healthy male subjects. The human metabolism and disposition data obtained will support future development and submissions of atuliflapon as a potential candidate drug for the treatment of cardiovascular, cardiorenal, and respiratory indications.

Safety and efficacy of the 5-lipoxygenase-activating protein inhibitor AZD5718 in patients with recent myocardial infarction: The phase 2a FLAVOUR study

BACKGROUND

Leukotrienes are pro-inflammatory vasoactive lipid mediators implicated in the pathophysiology of atherosclerotic cardiovascular disease. We studied the effect of the 5-lipoxygenase-activating protein inhibitor AZD5718 on leukotriene biosynthesis and coronary microvascular function in a single-blind, phase 2a study.

METHODS

Patients 7-28 days after myocardial infarction (±ST elevation), with <50% left anterior descending coronary artery stenosis and Thrombolysis in Myocardial Infarction flow grade ≥ 2 after percutaneous coronary intervention, were randomized 2:1:2 to once-daily AZD5718 200 mg or 50 mg, or placebo, in 4- and 12-week cohorts. Change in urine leukotriene E₄ (uLTE₄) was the primary endpoint, and coronary flow velocity reserve (CFVR; via echocardiography) was the key secondary endpoint.

RESULTS

Of 129 randomized patients, 128 received treatment (200 mg, n = 52; 50 mg, n = 25; placebo, n = 51). Statistically significant reductions in uLTE₄ levels of >80% were observed in both AZD5718 groups versus the placebo group at 4 and 12 weeks. No significant changes in CFVR were observed for AZD5718 versus placebo. Adverse events (AEs) occurred in 12/18, 3/6 and 6/13 patients receiving 200 mg, 50 mg and placebo, respectively, in the 4-week cohort, and in 27/34, 14/19 and 24/38 patients, respectively, in the 12-week cohort. Serious AEs in seven patients receiving AZD5718 and four receiving placebo were not treatment-related, and there were no deaths.

CONCLUSIONS

In patients with recent myocardial infarction, AZD5718 was well tolerated, and leukotriene biosynthesis was dose-dependently inhibited. No significant changes in CFVR were detected.

CLINICALTRIALS

gov identifier: NCT03317002.

Inflammatory Mediators in Atherosclerotic Vascular Remodeling

Atherosclerotic vascular disease remains the most common cause of ischemia, myocardial infarction, and stroke. Vascular function is determined by structural and functional properties of the arterial vessel wall, which consists of three layers, namely the adventitia, media, and intima. Key cells in shaping the vascular wall architecture and warranting proper vessel function are vascular smooth muscle cells in the arterial media and endothelial cells lining the intima. Pathological alterations of this vessel wall architecture called vascular remodeling can lead to insufficient vascular function and subsequent ischemia and organ damage. One major pathomechanism driving this detrimental vascular remodeling is atherosclerosis, which is initiated by endothelial dysfunction allowing the accumulation of intimal lipids and leukocytes. Inflammatory mediators such as cytokines, chemokines, and modified lipids further drive vascular remodeling ultimately leading to thrombus formation and/or vessel occlusion which can cause major cardiovascular events. Although it is clear that vascular wall remodeling is an elementary mechanism of atherosclerotic vascular disease, the diverse underlying pathomechanisms and its consequences are still insufficiently understood.

Mental Stress and Its Effects on Vascular Health

Coronary artery disease continues to be a major cause of morbidity and mortality despite significant advances in risk stratification and management. This has prompted the search for alternative nonconventional risk factors that may provide novel therapeutic targets. Psychosocial stress, or mental stress, has emerged as an important risk factor implicated in a higher incidence of cardiovascular events, and although our understanding of this far ranging and interesting phenomenon has developed greatly over recent times, there is still much to be learned regarding how to measure mental stress and how it may impact physical health. With the current coronavirus disease 2019 global pandemic and its incumbent lockdowns and social distancing, understanding the potentially harmful biological effects of stress related to life-changing events and social isolation has become even more important. In the current review our multidisciplinary team discusses stress from a psychosocial perspective and aims to define psychological stress as rigorously as possible; discuss the pathophysiologic mechanisms by which stress may mediate cardiovascular disease, with a particular focus to its effects on vascular health; outline existing methods and approaches to quantify stress by means of a vascular biomarker; outline the mechanisms whereby psychosocial stressors may have their pathologic effects ultimately transduced to the vasculature through the neuroendocrine immunologic axis; highlight areas for improvement to refine existing approaches in clinical research when studying the consequences of psychological stress on cardiovascular health; and discuss evidence-based therapies directed at reducing the deleterious effects of mental stress including those that target endothelial dysfunction. To this end we searched PubMed and Google Scholar to identify studies evaluating the relationship between mental or psychosocial stress and cardiovascular disease with a particular focus on vascular health. Search terms included "myocardial ischemia," "coronary artery disease," "mental stress," "psychological stress," "mental∗ stress∗," "psychologic∗ stress∗," and "cardiovascular disease∗." The search was limited to studies published in English in peer-reviewed journals between 1990 and the present day. To identify potential studies not captured by our database search strategy, we also searched studies listed in the bibliography of relevant publications and reviews.

Affinity ultrafiltration and UPLC-HR-Orbitrap-MS based screening of thrombin-targeted small molecules with anticoagulation activity from Poecilobdella manillensis

This study aims to screen potential anticoagulant components from leeches, a representative animal-sourced traditional Chinese medicine using thrombin (THR)-targeted ultrafiltration combined with ultrahigh performance liquid chromatography and high-resolution Orbitrap mass spectrometry (UPLC-HR-Orbitrap-MS). As a result, five small molecules in leech extract were discovered to interact with THR for the first time. Among them, two new compounds were isolated and their structures were identified by IR, HR-MS and NMR data. Furthermore, their THR inhibitory activity was confirmed with IC₅₀ values of 4.74 and 8.31 μM, respectively. In addition, molecular docking analysis showed that the active (catalytic) site of THR might be the possible binding site of the two hits. Finally, reverse screening analysis indicated that LTA4-H, ACE and ALOX5AP were potential anticoagulant targets of the two new compounds. This study will broaden our understanding of the medicinal substance basis in leeches and further contribute to the discovery and development of clinical anticoagulant drugs from leeches.

Montelukast Use Decreases Cardiovascular Events in Asthmatics

Cysteinyl leukotrienes are proinflammatory mediators with a clinically established role in asthma and a human genetic and preclinical role in cardiovascular pathology. Given that cardiovascular disease has a critical inflammatory component, the aim of this work was to conduct an observational study to verify whether the use of a cysteinyl leukotriene antagonist, namely, montelukast, may protect asthmatic patients from a major cardiovascular event and, therefore, represent an innovative adjunct therapy to target an inflammatory component in cardiovascular disease. We performed an observational retrospective 3-year study on eight hundred adult asthmatic patients 18 years or older in Albania, equally distributed into two cohorts, exposed or nonexposed to montelukast usage, matched by age and gender according to information reported in the data collection. Patients with a previous history of myocardial infarction or ischemic stroke were excluded. In summary, 37 (4.6%) of the asthmatic patients, 32 nonexposed, and five exposed to montelukast suffered a major cardiovascular event during the 3-year observation period. All the cardiovascular events, in either group, occurred among patients with an increased cardiovascular risk. Our analyses demonstrate that, independent from gender, exposure to montelukast remained a significant protective factor for incident ischemic events (78% or 76% risk reduction depending on type of analysis). The event-free Kaplan–Meier survival curves confirmed the lower cardiovascular event incidence in patients exposed to montelukast. Our data suggest that there is a potential preventative role of montelukast for incident cardiac ischemic events in the older asthmatic population, indicating a comorbidity benefit of montelukast usage in asthmatics by targeting cysteinyl leukotriene-driven cardiac disease inflammation.

A case-control study: Evaluating the role of leukotriene receptor antagonists in preventing the cardiovascular and cerebrovascular disease

INTRODUCTION

Leukotriene receptor antagonists (LTRAs) are used as a therapeutic alternative in asthmatic patients. Different animal studies indicate that LTRAs can decrease intimal hyperplasia after vascular injury, and have a protective role in cerebral ischemia.

OBJECTIVE

The aim of this study was to assess the role of leukotriene receptor antagonists in preventing the cardiovascular and ischemic stroke in humans.

MATERIAL AND METHOD

A matched case-control study with a follow up period of three years has been conducted, investigating the effect of the LTRAs in the myocardial infarct (MI) risk, and in the ischemic stroke (IS) risk in asthmatic patients from San Cecilio University Hospital of Granada, and from two Primary Health Care Centers of Granada.

RESULTS

59 cases with MI and 108 cases with IS were included in the study, each of them with an equal number of controls matched by age and sex in each of the two Health Care Centers. Unlike for MI risk, the treatment with LTRAs was associated with a slight trend in reducing the risk of stroke, in both of the primary care controls (Odds ratios: 0.74 (0.37-1.47); 0.82 (0.4-1.67), for the first, and the second Health Centers Controls, respectively), but without reaching a statistical significance.

CONCLUSIONS

The results did not confirm a protective effect of LTRAs on cardiovascular risk as suggested by different animal studies.

Effects of Psychological Stress on Vascular Physiology: Beyond the Current Imaging Signal

PURPOSE OF REVIEW

This review describes the effects of psychological stress on the physiology of the entire vascular system, from individual cellular components to macrovascular and microvascular responses, and highlights the importance of the vascular system in the context of current limitations in cardiac imaging for evaluation of the cardiovascular response to mental stress.

RECENT FINDINGS

The physiological responses that mediate vascular changes are based on evolutionary needs, but there is increasing evidence that the long-term consequences of psychological stress can precipitate the development and progression of cardiovascular disease (CVD). While there is an extensive body of literature describing localized physiological responses or overt cardiovascular manifestations, often framed within the organ-specific scope of cardiovascular imaging, there has not been a comprehensive description of the global vascular effects of psychological stress. Given the global nature of these processes, targeted cardiovascular imaging modalities may be insufficient. Here we approach the vascular response to mental stress systematically, describing the effects on the endothelium, vascular smooth muscle, and adventitia. We then address the mental stress effects on large vessels and the microvascular compartment, with a discussion of the role of microvascular resistance in the pathophysiology of mental stress-induced myocardial ischemia. Vascular responses to psychological stress involve complex physiological processes that are not fully characterized by routine cardiovascular imaging assessments. Future research incorporating standardized psychological assessments targeted toward vascular mechanisms of stress responses is required to guide the development of behavioral and therapeutic interventions.

Targeted anti-inflammatory therapy is a new insight for reducing cardiovascular events: A review from physiology to the clinic

Despite considerable progressions, cardiovascular disease (CVD) is still one of the major causes of mortality around the world, indicates an important and unmet clinical need. Recently, extensive studies have been performed on the role of inflammatory factors as either a major or surrogate factor in the pathophysiology of CVD. Epidemiological observations suggest the theory of the role of inflammatory mediators in the development of cardiovascular events. This may support the idea that targeted anti-inflammatory therapies, on the background of traditional validated medical therapies, can play a significant role in prevention and even reduction of cardiovascular disorders. Many randomized controlled trials have shown that drugs commonly useful for primary and secondary prevention of CVD have an anti-inflammatory mechanism. Further, many anti-inflammatory drugs are being examined because of their potential to reduce the risk of cardiovascular problems. In this study, we review the process of inflammation in the development of cardiovascular events, both in vivo and clinical evidence in immunotherapy for CVD.

Phase 1 Pharmacokinetic Study of AZD5718 in Healthy Volunteers: Effects of Coadministration With Rosuvastatin, Formulation and Food on Oral Bioavailability

AZD5718 is a first‐in‐class small‐molecule anti‐inflammatory drug with the potential to reduce the residual risk of cardiovascular events after myocardial infarction in patients receiving lipid‐lowering statin therapy. Leukotrienes are potent proinflammatory and vasoactive mediators synthesized in leukocytes via 5‐lipoxygenase and 5‐lipoxygenase‐activating protein (FLAP). AZD5718 is a FLAP inhibitor that dose‐dependently reduced leukotriene biosynthesis in a first‐in‐human study. We enrolled 12 healthy men in a randomized, open‐label, crossover, single‐dose phase 1 pharmacokinetic study of AZD5718 to investigate a potential drug‐drug interaction with rosuvastatin, and the effects of formulation and food intake (ClinicalTrials.gov identifier: NCT02963116). Rosuvastatin (10 mg) were absorbed more rapidly when coadministered with AZD5718 (200 mg), probably owing to weak inhibition of hepatic statin uptake, but relative bioavailability was unaffected (geometric least‐squares mean ratio [GMR], 100%; 90% confidence interval [CI], 86%‐116%). AZD5718 pharmacokinetics were unaffected by coadministration of rosuvastatin. AZD5718 (200 mg) was absorbed less rapidly when formulated as tablets than oral suspension, with reduced relative bioavailability (GMR, 72%; 90%CI, 64%‐80%). AZD5718 absorption was slower when 200‐mg tablets were taken after a high‐fat breakfast than after fasting, but relative bioavailability was unaffected (GMR, 96%; 90%CI, 87%‐106%). In post hoc pharmacodynamic simulations, plasma leukotriene B₄ levels were inhibited by >90% throughout the day following once‐daily AZD5718, regardless of formulation or administration with food. AZD5718 was well tolerated, with no severe or serious adverse events. These data supported the design of a phase 2a efficacy study of AZD5718 in patients with coronary artery disease.

Highly sensitive and specific LC–MS/MS method to determine endogenous leukotriene B4 levels in human plasma

Aim: To develop a high sensitivity and specific analytical method to measure endogenous levels of leukotriene B4 (LTB4) in human plasma. Methodology: LC–MS/MS and ELISA. Results: An LC–MS/MS method was developed with a sensitivity of 1.0 pg/ml, and within and between batch precision of <16% and <13% RSD, respectively. Conclusion: We have developed a sensitive LC–MS/MS method that can detect endogenous LTB4 in human plasma. The LC–MS/MS method displayed correlation with a commercial LTB4 ELISA when analyzing in ex vivo ionophore-stimulated blood samples. For untreated plasma this correlation was lost. Endogenous LTB4 was shown to be unstable in plasma during storage at -20°C and subject to stereoisomer formation. Neither of the assays could quantify endogenous plasma LTB4 in samples stored for long term.

Celecoxib aggravates atherogenesis and upregulates leukotrienes in ApoE-/- mice and lipopolysaccharide-stimulated RAW264.7 macrophages

BACKGROUND AND AIMS

COX-2-selective inhibitors have been associated with an increased risk of cardiovascular complications, and their impact on atherosclerosis (AS) remains controversial. The proinflammatory COX-2 and 5-LO pathways both play essential roles in AS and related cardiovascular diseases. Previous clinical studies have provided evidence of the ability of COX-2-selective inhibitors to shunt AA metabolism from the COX-2 pathway to the 5-LO pathway. In this study, the effects of celecoxib, a selective COX-2 inhibitor, on AS and the COX-2 and 5-LO pathways were investigated in vivo and in vitro.

METHODS

Male ApoE^-/- mice fed a western-type diet for 18 weeks and cultured mouse RAW264.7 macrophages stimulated with 1 μg/mL LPS for 24 h were used in this study.

RESULTS

In ApoE^-/- mice, intragastric administration of celecoxib (80 mg/kg/d) for 18 weeks significantly increased aortic atherosclerotic lesion area but had no effect on hyperlipidemia. In addition, celecoxib significantly lowered TNF-α and PGE₂ levels but increased both LTB₄ and CysLTs levels in aortic tissues. In LPS-stimulated RAW264.7 macrophages, pretreatment with 8 μmol/L celecoxib for 1 h significantly lowered the TNF-α, NO, and PGE₂ levels but increased the LTB₄ and CysLTs levels. Celecoxib also decreased the protein and mRNA expression of COX-2 but increased the expression of 5-LO and LTC₄S in both ApoE^-/- mouse aortic tissues and LPS-stimulated RAW264.7 macrophages.

CONCLUSION

The COX-2-selective inhibitor celecoxib can aggravate atherogenesis, an effect that may be related to upregulation of LTs via a 5-LO pathway shunt.

Potential role of leukotriene receptor antagonists in reducing cardiovascular and cerbrovascular risk: A systematic review of human clinical trials and in vivo animal studies

BACKGROUND

Leukotrienes are important lipid mediators of inflammation arising from arachidonic acid cascade. They are implicated in vascular inflammation and produced in different pathologic conditions as atherosclerosis, stroke and myocardial infarction. Different studies have investigated the role of leukotriene receptor antagonist (LTRA) in reducing some cardiovascular events, especially in animals. We conducted a systematic review of both in vivo animal and human studies to determine the potential role of leukotriene receptor antagonist in reducing cardiovascular and cerebrovascular events.

METHODS

Data sources: Pubmed, Embase and Cochrane database.

DATA EXTRACTION

Two reviewers independently screened potentially eligible articles and extracted relevant data.

RESULTS

A total of 28 studies were included, of which 26 were conducted in animals, and 2 in humans.

CONCLUSIONS

All animal studies reported that using a leukotriene receptor antagonist brings to a reduction of either myocardial infarction, ischemic stroke, or atherosclerosis risk. Similar results were obtained from two clinical trials on humans, suggesting a potential role of montelukast in reducing some cardiovascular diseases.

Initial Clinical Experience with AZD5718, a Novel Once Daily Oral 5-Lipoxygenase Activating Protein Inhibitor

We evaluated safety, tolerability, pharmacokinetics, and pharmacodynamics of AZD5718, a novel 5-lipooxygenase activating protein (FLAP) inhibitor, in a randomized, single-blind, placebo-controlled, first-in-human (FIH) study consisting of single and multiple ascending dosing (SAD and MAD) for 10 days in healthy subjects. Target engagement was measured by ex vivo calcium ionophore stimulated leukotriene B (LTB₄ ) production in whole blood and endogenous leukotriene E (LTE₄ ) in urine. No clinically relevant safety and tolerability findings were observed. The AZD5718 was rapidly absorbed and plasma concentrations declined biphasically with a mean terminal half-life of 10-12 h. Steady-state levels were achieved after ∼3 days. After both SADs and MADs, a dose/concentration-effect relationship between both LTB₄ and LTE₄ vs. AZD5718 exposure was observed with concentration of half inhibition (IC₅₀ ) values in the lower nM range. Based on obtained result, AZD5718 is considered as a suitable drug candidate for future evaluation in patients with coronary artery disease (CAD).

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.

Capturing LTA4 hydrolase in action: Insights to the chemistry and dynamics of chemotactic LTB4 synthesis

Human leukotriene (LT) A₄ hydrolase/aminopeptidase (LTA₄H) is a bifunctional enzyme that converts the highly unstable epoxide intermediate LTA₄ into LTB₄, a potent leukocyte activating agent, while the aminopeptidase activity cleaves and inactivates the chemotactic tripeptide Pro-Gly-Pro. Here, we describe high-resolution crystal structures of LTA₄H complexed with LTA₄, providing the structural underpinnings of the enzyme's unique epoxide hydrolase (EH) activity, involving Zn²⁺, Y383, E271, D375, and two catalytic waters. The structures reveal that a single catalytic water is involved in both catalytic activities of LTA₄H, alternating between epoxide ring opening and peptide bond hydrolysis, assisted by E271 and E296, respectively. Moreover, we have found two conformations of LTA₄H, uncovering significant domain movements. The resulting structural alterations indicate that LTA₄ entrance into the active site is a dynamic process that includes rearrangement of three moving domains to provide fast and efficient alignment and processing of the substrate. Thus, the movement of one dynamic domain widens the active site entrance, while another domain acts like a lid, opening and closing access to the hydrophobic tunnel, which accommodates the aliphatic tale of LTA₄ during EH reaction. The enzyme-LTA₄ complex structures and dynamic domain movements provide critical insights for development of drugs targeting LTA₄H.

Lipid droplets in activated mast cells - a significant source of triglyceride-derived arachidonic acid for eicosanoid production

Mast cells are potent effectors of immune reactions and key players in various inflammatory diseases such as atherosclerosis, asthma, and rheumatoid arthritis. The cellular defense response of mast cells represents a unique and powerful system, where external signals can trigger cell activation resulting in a stimulus-specific and highly coordinated release of a plethora of bioactive mediators. The arsenal of mediators encompasses preformed molecules stored in cytoplasmic secretory granules, as well as newly synthesized proteinaceous and lipid mediators. The release of mediators occurs in strict chronological order and requires proper coordination between the endomembrane system and various enzymatic machineries. For the generation of lipid mediators, cytoplasmic lipid droplets have been shown to function as a major intracellular pool of arachidonic acid, the precursor for eicosanoid biosynthesis. Recent studies have revealed that not only phospholipids in mast cell membranes, but also triglycerides in mast cell lipid droplets are a substrate source for eicosanoid formation. The present review summarizes current knowledge about mast cell lipid droplet biology, and discusses expansions and challenges of traditional mechanistic models for eicosanoid production.

Recent advances for FLAP inhibitors

A number of FLAP inhibitors have been progressed to clinical trials for respiratory and other inflammatory indications but so far no drug has reached the market. With this Digest we assess the opportunity to develop FLAP inhibitors for indications beyond respiratory disease, and in particular for atherosclerotic cardiovascular disease. We also show how recently disclosed FLAP inhibitors have structurally evolved from the first generation FLAP inhibitors paving the way for new compound classes.

Anti-inflammatory therapies for atherosclerosis

The view of atherosclerosis as an inflammatory disease has emerged from observations of immune activation and inflammatory signalling in human atherosclerotic lesions, from the definition of inflammatory biomarkers as independent risk factors for cardiovascular events, and from evidence of low-density lipoprotein-induced immune activation. Studies in animal models of hyperlipidaemia have also supported the beneficial effects of countering inflammation to delay atherosclerosis progression. Specific inflammatory pathways with relevance to human diseases have been identified, and inhibitors of these pathways are either already in use for the treatment of other diseases, or are under development and evaluation. These include 'classic' drugs (such as allopurinol, colchicine, and methotrexate), biologic therapies (for example tumour necrosis factor inhibitors and IL-1 neutralization), as well as targeting of lipid mediators (such as phospholipase inhibitors and antileukotrienes) or intracellular pathways (inhibition of NADPH oxidase, p38 mitogen-activated protein kinase, or phosphodiesterase). The evidence supporting the use of anti-inflammatory therapies for atherosclerosis is mainly based on either observational or small interventional studies evaluating surrogate markers of disease activity. Nevertheless, these data are crucial to understand the role of inflammation in atherosclerosis, and to design randomized controlled studies to evaluate the effect of specific anti-inflammatory strategies on cardiovascular outcomes.

Mammalian lipoxygenases and their biological relevance

Lipoxygenases (LOXs) form a heterogeneous class of lipid peroxidizing enzymes, which have been implicated not only in cell proliferation and differentiation but also in the pathogenesis of various diseases with major public health relevance. As other fatty acid dioxygenases LOXs oxidize polyunsaturated fatty acids to their corresponding hydroperoxy derivatives, which are further transformed to bioactive lipid mediators (eicosanoids and related substances). On the other hand, lipoxygenases are key players in the regulation of the cellular redox homeostasis, which is an important element in gene expression regulation. Although the first mammalian lipoxygenases were discovered 40 years ago and although the enzymes have been well characterized with respect to their structural and functional properties the biological roles of the different lipoxygenase isoforms are not completely understood. This review is aimed at summarizing the current knowledge on the physiological roles of different mammalian LOX-isoforms and their patho-physiological function in inflammatory, metabolic, hyperproliferative, neurodegenerative and infectious disorders. This article is part of a Special Issue entitled "Oxygenated metabolism of PUFA: analysis and biological relevance".

Leukotriene B4 levels in human atherosclerotic plaques and abdominal aortic aneurysms

BACKGROUND

Leukotriene B4 (LTB4) has been associated with the initiation and progression of atherosclerosis and abdominal aortic aneurysm (AAA) formation. However, associations of LTB4 levels with tissue characteristics and adverse clinical outcome of advanced atherosclerosis and AAA are scarcely studied. We hypothesized that LTB4 levels are associated with a vulnerable plaque phenotype and adverse clinical outcome. Furthermore, that LTB4 levels are associated with inflammatory AAA and adverse clinical outcome.

METHODS

Atherosclerotic plaques and AAA specimens were selected from two independent databases for LTB4 measurements. Plaques were isolated during carotid endarterectomy from asymptomatic (n = 58) or symptomatic (n = 317) patients, classified prior to surgery. LTB4 levels were measured without prior lipid extraction and levels were corrected for protein content. LTB4 levels were related to plaque phenotype, baseline patient characteristics and clinical outcome within three years following surgery. Seven non-diseased mammary artery specimens served as controls. AAA specimens were isolated during open repair, classified as elective (n = 189), symptomatic (n = 29) or ruptured (n = 23). LTB4 levels were measured similar to the plaque measurements and were related to tissue characteristics, baseline patient characteristics and clinical outcome. Twenty-six non-diseased aortic specimens served as controls.

RESULTS

LTB4 levels corrected for protein content were not significantly associated with histological characteristics specific for vulnerable plaques or inflammatory AAA as well as clinical presentation. Moreover, it could not predict secondary manifestations independently investigated in both databases. However, LTB4 levels were significantly lower in controls compared to plaque (p = 0.025) or AAA (p = 0.017).

CONCLUSIONS

LTB4 levels were not associated with a vulnerable plaque phenotype or inflammatory AAA or clinical presentation. This study does not provide supportive evidence for a role of LTB4 in atherosclerotic plaque destabilization or AAA expansion. However, these data should be interpreted with care, since LTB4 measurements were performed without prior lipid extractions.

Indirubin-3'-monoxime exerts a dual mode of inhibition towards leukotriene-mediated vascular smooth muscle cell migration

Aims

The small molecule indirubin-3′-monoxime (I3MO) has been shown to inhibit vascular smooth muscle cell (VSMC) proliferation and neointima formation in vivo. The influence of I3MO on VSMC migration and vascular inflammation, two additional key players during the onset of atherosclerosis and restenosis, should be investigated.

Methods and results

We examined the influence of I3MO on VSMC migration, with focus on monocyte-derived leukotrienes (LTs) and platelet-derived growth factors (PDGFs) as elicitors. Exogenous LTB4 and cysteinyl leukotrienes as well as LT-enriched conditioned medium of activated primary human monocytes induced VSMC migration, which was inhibited by I3MO. I3MO also blunted migration of VSMC stimulated with the PDGF, the strongest motogen tested in this study. Induction of haem oxygenase 1 accounted for this anti-migratory activity of I3MO in VSMC. Notably, I3MO not only interfered with the migratory response in VSMC, but also suppressed the production of pro-migratory LT in monocytes. Conditioned media from monocytes that were activated in the presence of I3MO failed to induce VSMC migration. In cell-based and cell-free assays, I3MO selectively inhibited 5-lipoxygenase (5-LO), the key enzyme in LT biosynthesis, with an IC₅₀ in the low micromolar range.

Conclusion

Our study reveals a novel dual inhibitory mode of I3MO on LT-mediated VSMC migration: (i) I3MO interferes with pro-migratory signalling in VSMC and (ii) I3MO suppresses LT biosynthesis in monocytes by direct inhibition of 5-LO. These inhibitory actions on both migratory stimulus and response complement the previously demonstrated anti-proliferative properties of I3MO and may further promote I3MO as promising vasoprotective compound.

Targeting leukotriene B4 in inflammation

INTRODUCTION

Leukotriene (LT) B(4) is a powerful proinflammatory lipid mediator and triggers adherence to the endothelium, activates and recruits leukocytes to the site of injury. When formed in excess, LTB(4) plays a pathogenic role and may sustain chronic inflammation in diseases such as asthma, rheumatoid arthritis, and inflammatory bowel disease. Recent investigations have also indicated that LTB(4) is involved in cardiovascular diseases.

AREAS COVERED

As the 5-lipoxygenase pathway involves several discrete, tightly coupled, enzymes, which convert the substrate, 'step by step', into bioactive products, several different strategies have been used to target LTB(4) as a means to treat inflammation. Here, we discuss recent findings regarding the development of selective enzyme inhibitors and antagonists for LTB(4) receptors, as well as their application in preclinical and clinical studies.

EXPERT OPINION

Components of the 5-lipoxygenase pathway have received considerable attention as candidate drug targets resulting in one new class of medications against asthma, that is, the antileukotrienes. However, efforts to specifically target LTB(4) have not yet been fruitful in the clinical setting, in spite of very promising preclinical data. Recently, crystal structures along with hitherto unknown functions of key enzymes in the leukotriene cascade have emerged, offering new opportunities for drug development and, with time, pharmacological intervention in LTB(4)-mediated pathologies.

A review on leukotrienes and their receptors with reference to asthma

OBJECTIVE AND METHODS

Leukotrienes (LTs) including cysteinyl leukotrienes (CysLTs) and LTB4 are the most potent inflammatory lipid mediators and play a central role in the pathophysiology of asthma and other inflammatory diseases. These biological molecules mediate a plethora of contractile and inflammatory responses through specific interaction with distinct G protein-coupled receptors (GPCRs). The main objective of this review is to present an overview of the biological effects of CysLTs and their receptors, along with the current knowledge of mechanisms and role of LTs in the pathogenesis of asthma.

RESULTS

CysLTs including LTC4, LTD4 and LTE4 are ligands for CysLT1 and CysLT2 receptors, and LTB4 is the agonist for BLT1 and BLT2 receptors. The role of CysLT1 receptor is well established, and most of the pathophysiological effects of CysLTs in asthma are mediated by CysLT1 receptor. Several CysLT1 antagonists have been developed to date and are currently in clinical practice. Most common among them are classical CysLT1 receptor antagonists such as montelukast, zafirlukast, pranlukast, pobilukast, iralukast, cinalukast and MK571. The pharmacological role of CysLT2 receptor, however, is less defined and there is no specific antagonist available so far. The recent demonstration that mice lacking both known CysLT receptors exhibit full/augmented response to CysLT points to the existence of additional subtypes of CysLT receptors. LTB4, on the other hand, is another potent inflammatory leukotriene, which acts as a strong chemoattractant for neutrophils, but weaker for eosinophils. LTB4 is known to play an important role in the development of airway hyper-responsiveness in severe asthma. However there is no LTB4 antagonist available in clinic to date.

CONCLUSION

This review gives a recent update on the LTs including their biosynthesis, biological effects and the role of anti-LTs in the treatment of asthma. It also discusses about the possible existence of additional subtypes of CysLT receptors.

Coronary flow reserve from mouse to man--from mechanistic understanding to future interventions

Myocardial ischemia is recognized as an important mechanism increasing the risk for cardiovascular events in both symptomatic and asymptomatic patients. In addition to obstructive coronary diseases, systemic inflammation, macro- and microvascular function are additional important mechanisms contributing to the ischemic myocardium. Accumulating evidence indicates that coronary flow reserve (CFR) is a quantitative measurement of ischemia including integrated information on structure and function of the coronary artery at all levels. Not surprisingly, CFR has been shown to confer strong prognostic value for hard cardiovascular (CV) events in a number of relevant patient cohorts. Using high-resolution imaging, it is now possible to study coronary arteries from mouse to man. Therefore, CFR may be an important translational tool to risk-stratify patients and to perform both preclinical and clinical proof-of-concept studies before investing in large-scale outcome trials, thus improving the translational value for novel CV targets.

Adipose tissue arachidonic acid content is associated with the expression of 5-lipoxygenase in atherosclerotic plaques

Background

The content of arachidonic acid in adipose tissue is positively associated with the risk of myocardial infarction, whereas the content of eicosapentaenoic acid in adipose tissue has been reported to be negatively associated with the risk of myocardial infarction. Both arachidonic acid and eicosapentaenoic acid are substrates for the synthesis of pro-inflammatory leukotrienes and leukotrienes derived from eicosapentaenoic acid are generally much less potent. In this study we hypothesized that a high content of arachidonic acid in adipose tissue would reflect a high formation of arachidonic acid derived leukotrienes and a high expression of 5-lipoxygenase in atherosclerotic plaques. Likewise, we hypothesized that a high content of eicosapentaenoic acid in adipose tissue would reflect a low formation of arachidonic acid derived leukotrienes and a low expression of 5-lipoxygenase in plaques.

Methods

In a cross sectional study we included 45 consecutive subjects undergoing femoral thrombendarterectomy. The expression of 5-lipoxygenase in plaques was assessed by a semi-automated image analysis computer programme after immunohistochemical staining with mono-clonal 5-lipoxygenase antibodies. Leukotriene B₄ and cysteinyl leukotriene formation from stimulated femoral artery plaques was quantified using ELISA methods. The fatty acid content of adipose tissue biopsies from the thigh was analyzed using gas chromatography. Associations between variables were assessed by Pearson correlations and were further explored in a multivariable linear regression model adjusting for potential confounders.

Results

A high content of arachidonic acid in adipose tissue was associated with a higher expression of 5-lipoxygenase in plaques (r = 0.32, p = 0.03), but no significant associations with leukotriene B₄ (r = 0.22, p = 0.14) and cysteinyl leukotriene (r = −0.11, p = 0.46) formation was seen. No significant associations were found between the content of eicosapentaenoic acid in adipose tissue and 5-lipoxygenase expression or leukotriene formation in plaque.

Conclusions

Adipose tissue arachidonic acid contents correlated positively with the expression of 5-lipoxygenase in plaques. This association might represent a causal link between adipose tissue arachidonic acid and the risk of myocardial infarction but confirmatory studies are needed.

The leukotrienes: immune-modulating lipid mediators of disease

The leukotrienes are important lipid mediators with immune modulatory and proinflammatory properties. Classical bioactions of leukotrienes include chemotaxis, endothelial adherence, and activation of leukocytes, chemokine production, as well as contraction of smooth muscles in the microcirculation and respiratory tract. When formed in excess, these compounds play a pathogenic role in several acute and chronic inflammatory diseases, such as asthma, rheumatoid arthritis, and inflammatory bowel disease. An increasing number of diseases have been linked to inflammation implicating the leukotrienes as potential mediators. For example, recent investigations using genetic, morphological, and biochemical approaches have pointed to the involvement of leukotrienes in cardiovascular diseases including atherosclerosis, myocardial infarction, stroke, and abdominal aortic aneurysm. Moreover, new insights have changed our previous notion of leukotrienes as mediators of inflammatory reactions to molecules that can fine-tune the innate and adaptive immune response. Here, we review the most recent understanding of the leukotriene cascade with emphasis on recently identified roles in immune reactions and pathophysiology.

Cysteinyl leukotriene signaling aggravates myocardial hypoxia in experimental atherosclerotic heart disease

Background

Cysteinyl-leukotrienes (cys-LT) are powerful spasmogenic and immune modulating lipid mediators involved in inflammatory diseases, in particular asthma. Here, we investigated whether cys-LT signaling, in the context of atherosclerotic heart disease, compromises the myocardial microcirculation and its response to hypoxic stress. To this end, we examined Apoe^−/− mice fed a hypercholesterolemic diet and analysed the expression of key enzymes of the cys-LT pathway and their receptors (CysLT1/CysLT2) in normal and hypoxic myocardium as well as the potential contribution of cys-LT signaling to the acute myocardial response to hypoxia.

Methods and principal findings

Myocardial biopsies from Apoe^−/− mice demonstrated signs of chronic inflammation with fibrosis, increased apoptosis and expression of IL-6, as compared to biopsies from C57BL/6J control mice. In addition, we found increased leukotriene C₄ synthase (LTC₄S) and CysLT1 expression in the myocardium of Apoe^−/− mice. Acute bouts of hypoxia further induced LTC₄S expression, increased LTC₄S enzyme activity and CysLT1 expression, and were associated with increased extension of hypoxic areas within the myocardium. Inhibition of cys-LT signaling by treatment with montelukast, a selective CysLT1 receptor antagonist, during acute bouts of hypoxic stress reduced myocardial hypoxic areas in Apoe^−/− mice to levels equal to those observed under normoxic conditions. In human heart biopsies from 14 patients with chronic coronary artery disease mRNA expression levels of LTC₄S and CysLT1 were increased in chronic ischemic compared to non-ischemic myocardium, constituting a molecular basis for increased cys-LT signaling.

Conclusion

Our results suggest that CysLT1 antagonists may have protective effects on the hypoxic heart, and improve the oxygen supply to areas of myocardial ischemia, for instance during episodes of sleep apnea.

Leukotrienes as modifiers of preclinical atherosclerosis?

Preclinical atherosclerosis represents a crucial period associated with several pathophysiological reactions in the vascular wall. Failure to diagnose preclinical atherosclerosis at this stage misses a major opportunity to prevent the long-term consequences of this disease. Surrogate biological and structural vascular markers are available to determine the presence and the extension of preclinical vascular injury in the general population. Examples of surrogate markers are carotid intima media thickness and biomarkers including high-sensitivity C-reactive protein, cell adhesion molecules and matrix metalloproteinases, and leukotrienes. Recently, leukotrienes have been implicated as mediators, biomarkers, and possible therapeutic targets in the context of subclinical atherosclerosis. The aim of this short paper is to focus on the relation between preclinical atherosclerosis and leukotrienes, with particular attention to the recent development on the use of leukotriene modifiers in the treatment of atherosclerosis.

Cysteinyl leukotriene signaling through perinuclear CysLT(1) receptors on vascular smooth muscle cells transduces nuclear calcium signaling and alterations of gene expression

Leukotrienes are pro-inflammatory mediators that are locally produced in coronary atherosclerotic plaques. The response induced by cysteinyl leukotrienes (CysLT) in human coronary arteries may be altered under pathological conditions, such as atherosclerosis. The aim of the present study was to elucidate cysteinyl leukotriene signaling in vascular smooth muscle cells (SMCs) and the effects of inflammation on this process. Immunohistochemical analysis of human carotid endarterectomy samples revealed that the CysLT₁ leukotriene receptor was expressed in areas that also stained positive for α-smooth muscle actin. In human coronary artery smooth muscle cells, lipopolysaccharide significantly upregulated the CysLT₁ receptor and significantly enhanced the changes in intracellular calcium induced by leukotriene C₄ (LTC₄). In these cells, the CysLT₁ receptor exhibited a perinuclear expression, and LTC₄ stimulation predominantly enhanced nuclear calcium increase, which was significantly inhibited by the CysLT₁ receptor antagonist MK-571. Microarray analysis revealed, among a number of significantly upregulated genes after 24 h stimulation of human coronary artery smooth muscle cells with LTC₄, a 5-fold increase in mRNA levels for plasminogen activator inhibitor (PAI)-2. The LTC₄-induced increase in PAI-2 expression was confirmed by real-time quantitative PCR and ELISA and was inhibited by the CysLT₁ receptor antagonist MK-571 and by calcium chelators. In summary, pro-inflammatory stimulation of vascular SMCs upregulated a perinuclear CysLT₁ receptor expression coupled to nuclear calcium signaling and changes in gene expression, such as upregulation of PAI-2. Taken together, these findings suggest a role of nuclear CysLT₁ receptor signaling in vascular SMCs inducing gene expression patterns associated with atherosclerosis.

Disruption of the 5-lipoxygenase pathway attenuates atherogenesis consequent to COX-2 deletion in mice

Suppression of cyclooxygenase 2 (COX-2)-derived prostacyclin (PGI(2)) is sufficient to explain most elements of the cardiovascular hazard from nonsteroidal antinflammatory drugs (NSAIDs). However, randomized trials are consistent with the emergence of cardiovascular risk during chronic dosing with NSAIDs. Although deletion of the PGI(2) receptor fosters atherogenesis, the importance of COX-2 during development has constrained the use of conventional knockout (KO) mice to address this question. We developed mice in which COX-2 was deleted postnatally, bypassing cardiorenal defects exhibited by conventional KOs. When crossed into ApoE-deficient hyperlipidemic mice, COX-2 deletion accelerated atherogenesis in both genders, with lesions exhibiting leukocyte infiltration and phenotypic modulation of vascular smooth muscle cells, as reflected by loss of α-smooth muscle cell actin and up-regulation of vascular cell adhesion molecule-1. Stimulated peritoneal macrophages revealed suppression of COX-2-derived prostanoids and augmented 5-lipoxygenase product formation, consistent with COX-2 substrate rediversion. Although deletion of the 5-lipoxygenase activating protein (FLAP) did not influence atherogenesis, it attenuated the proatherogeneic impact of COX-2 deletion in hyperlipidemic mice. Chronic administration of NSAIDs may increasingly confer a cardiovascular hazard on patients at low initial risk. Promotion of atherogenesis by postnatal COX-2 deletion affords a mechanistic explanation for this observation. Coincident inhibition of FLAP may offer an approach to attenuating such a risk from NSAIDs.

5-Lipoxygenase metabolic contributions to NSAID-induced organ toxicity

Cyclooxygenase (COX)-1, COX-2, and 5-lipoxygenase (5-LOX) enzymes produce effectors of pain and inflammation in osteoarthritis (OA) and many other diseases. All three enzymes play a key role in the metabolism of arachidonic acid (AA) to inflammatory fatty acids, which contribute to the deterioration of cartilage. AA is derived from both phospholipase A(2) (PLA(2)) conversion of cell membrane phospholipids and dietary consumption of omega-6 fatty acids. Nonsteroidal antiinflammatory drugs (NSAIDs) inhibit the COX enzymes, but show no anti-5-LOX activity to prevent the formation of leukotrienes (LTs). Cysteinyl LTs, such as LTC(4), LTD(4), LTE(4), and leukoattractive LTB(4) accumulate in several organs of mammals in response to NSAID consumption. Elevated 5-LOX-mediated AA metabolism may contribute to the side-effect profile observed for NSAIDs in OA. Current therapeutics under development, so-called "dual inhibitors" of COX and 5-LOX, show improved side-effect profiles and may represent a new option in the management of OA.

International Union of Basic and Clinical Pharmacology. LXXXIV: leukotriene receptor nomenclature, distribution, and pathophysiological functions

The seven-transmembrane G protein-coupled receptors activated by leukotrienes are divided into two subclasses based on their ligand specificity for either leukotriene B(4) or the cysteinyl leukotrienes (LTC(4), LTD(4), and LTE(4)). These receptors have been designated BLT and CysLT receptors, respectively, and a subdivision into BLT(1) and BLT(2) receptors and CysLT(1) and CysLT(2) receptors has been established. However, recent findings have also indicated the existence of putative additional leukotriene receptor subtypes. Furthermore, other ligands interact with the leukotriene receptors. Finally, leukotrienes may also activate other receptor classes, such as purinergic receptors. The aim of this review is to provide an update on the pharmacology, expression patterns, and pathophysiological roles of the leukotriene receptors as well as the therapeutic developments in this area of research.

Removal characteristics of wipe devices under various conditions

Understanding the removal factor for specific conditions is essential to estimate removable surface contamination levels by wiping. The removal characteristics of dry foamed polystyrene pads and filter paper applied to polyvinyl chloride flooring are investigated using C-thymidine under various conditions (i.e., weight of contaminants, wax coating, temperature and humidity). Eight wipes were performed per flooring piece with a uniformly deposited contaminant to estimate the total removable surface contamination. The wipe devices were pressed against the surface by 2 kg-force with fingertips. The first wipe ratio (the ratio of the activity removed by the first wipe to the activity removed by eight wipes) from flooring on which was deposited 500 microg mL of C-thymidine solution varies between 24% and 71% for polystyrene pads and between 33% and 83% for filter papers, depending on the atmospheric humidity and temperature. For deposition concentrations of 1 microg mL, the mean first wipe ratio using polystyrene pads, which are almost constant vs. humidity and temperature, are 68% and 24% for waxed and unwaxed surfaces, respectively. Under the same conditions, the mean first wipe ratio for filter paper varied with both the surface and the environmental conditions. The total recovery (the ratio of the total activity removed by eight wipes to the total deposited activity) for deposition concentrations of 500 microg mL tended to increase with humidity for both wiping devices. The total recovery for deposition concentrations of 1 microg mL is generally low. The first wipe ratio in the lowest case with foamed polystyrene pads in this study was 19%. In that case, the total removable activity is speculated to increase from the sum of eight wipes, if additional wipes are performed. Therefore, the theoretical value of 0.1 recommended by ISO for the removal factor is appropriate when wiping polyvinyl chloride flooring using foamed polystyrene pads.

Pharmacological characterization of the first potent and selective antagonist at the cysteinyl leukotriene 2 (CysLT(2)) receptor

BACKGROUND AND PURPOSE

Cysteinyl leukotrienes (CysLTs) have been implicated in the pathophysiology of inflammatory and cardiovascular disorders. Their actions are mediated by CysLT(1) and CysLT(2) receptors. Here we report the discovery of 3-({[(1S,3S)-3-carboxycyclohexyl]amino}carbonyl)-4-(3-{4-[4-(cyclo-hexyloxy)butoxy]phenyl}propoxy) benzoic acid (HAMI3379), the first potent and selective CysLT(2) receptor antagonist.

EXPERIMENTAL APPROACH

Pharmacological characterization of HAMI3379 was performed using stably transfected CysLT(1) and CysLT(2) receptor cell lines, and isolated, Langendorff-perfused, guinea pig hearts.

KEY RESULTS

In a CysLT(2) receptor reporter cell line, HAMI3379 antagonized leukotriene D(4)- (LTD(4)-) and leukotriene C(4)- (LTC(4)-) induced intracellular calcium mobilization with IC(50) values of 3.8 nM and 4.4 nM respectively. In contrast, HAMI3379 exhibited very low potency on a recombinant CysLT(1) receptor cell line (IC(50) > 10 000 nM). In addition, HAMI3379 did not exhibit any agonistic activity on both CysLT receptor cell lines. In binding studies using membranes from the CysLT(2) and CysLT(1) receptor cell lines, HAMI3379 inhibited [(3)H]-LTD(4) binding with IC(50) values of 38 nM and >10 000 nM respectively. In isolated Langendorff-perfused guinea pig hearts HAMI3379 concentration-dependently inhibited and reversed the LTC(4)-induced perfusion pressure increase and contractility decrease. The selective CysLT(1) receptor antagonist zafirlukast was found to be inactive in this experimental setting.

CONCLUSIONS AND IMPLICATIONS

HAMI3379 was identified as a potent and selective CysLT(2) receptor antagonist, which was devoid of CysLT receptor agonism. Using this compound, we showed that the cardiac effects of CysLTs are predominantly mediated by the CysLT(2) receptor.

Oxidative risk for atherothrombotic cardiovascular disease

In the vasculature, reactive oxidant species, including reactive oxygen, nitrogen, or halogenating species, and thiyl, tyrosyl, or protein radicals may oxidatively modify lipids and proteins with deleterious consequences for vascular function. These biologically active free radical and nonradical species may be produced by increased activation of oxidant-generating sources and/or decreased cellular antioxidant capacity. Once formed, these species may engage in reactions to yield more potent oxidants that promote transition of the homeostatic vascular phenotype to a pathobiological state that is permissive for atherothrombogenesis. This dysfunctional vasculature is characterized by lipid peroxidation and aberrant lipid deposition, inflammation, immune cell activation, platelet activation, thrombus formation, and disturbed hemodynamic flow. Each of these pathobiological states is associated with an increase in the vascular burden of free radical species-derived oxidation products and, thereby, implicates increased oxidant stress in the pathogenesis of atherothrombotic vascular disease.

Common variants of four bilirubin metabolism genes and their association with serum bilirubin and coronary artery disease in Chinese Han population

OBJECTIVES

Studies have revealed an inverse relationship between serum total bilirubin (TBIL) levels and coronary artery disease (CAD). This study investigated the genetic variants of four bilirubin metabolism genes--heme oxygenase-1 (HMOX1), biliverdin reductase A (BLVRA), solute carrier organic anion transporter family member 1B1 (SLCO1B1), and uridine diphosphate glycosyltransferase 1A1 (UGT1A1)--in relation to TBIL levels and CAD.

METHODS AND RESULTS

Thirty-five common single nucleotide polymorphisms (SNPs) were genotyped in 2380 unrelated Han participants who underwent angiocardiography at hospitals in Shanghai, China. Only three genetic variants--rs4399719 (UGT1A1 T-2473G), rs887829 (UGT1A1 G-364A), and rs4148323 (UGT1A1 G211A)--were associated with TBIL levels (each P<0.001). Four significant associations with CAD were detected after controlling age and the false discovery rate at 15%: the recessive effect of SNP rs887829 (UGT1A1 G-364A) [age-adjusted odds ratio (OR): 0.24; 95% confidence interval (CI): 0.10-0.60; P=0.0014] and dominant effect of rs4149013 (SLCO1B1 A-12099G) (age-adjusted OR: 0.70; 95% CI: 0.55-0.91; P=0.0069) on male CAD, and the additive effects of rs2877262 (BLVRA G+1238/in6C) (age-adjusted OR: 0.73; 95% CI: 0.59-0.89; P=0.0021) and rs2690381 (BLVRA G+2613/in6A) (age-adjusted OR: 0.70; 95% CI: 0.56-0.86; P=0.0008) on female CAD. SNPs rs2877262 and rs2690381 were both in a linkage disequilibrium block within BLVRA with r greater than 0.750. Correspondingly, this block was identified to be associated with female CAD.

CONCLUSION

Our study provides genetic evidences for the difference in the impact of these four bilirubin metabolism genes on TBIL levels and CAD.

Leukotriene C4 synthase and ischemic cardiovascular disease and obstructive pulmonary disease in 13,000 individuals

Ischemic cardiovascular disease and obstructive pulmonary disease involve inflammation. Leukotrienes may be important pro-inflammatory mediators. We tested the hypothesis that the (-1072)G > A and (-444)A > C promoter polymorphisms of leukotriene C4 synthase confer risk of transient ischemic attack (TIA), ischemic stroke, ischemic heart disease (IHD), asthma, and chronic obstructive pulmonary disease (COPD). We genotyped individuals from the Danish general population, the Copenhagen City Heart Study, and Danish patients with IHD/coronary atherosclerosis, the Copenhagen Ischemic Heart Disease Study. We used prospective (n = 10,386), cross-sectional (n = 10,386), and case-control (n = 2392 + 5012) designs. Allele frequency was 0.07 for (-1072)A and 0.29 for (-444)C. Cumulative incidence for TIA was higher for (-1072)AA versus GG genotype (log-rank: p < 0.001), and lower for (-444)CC versus AA genotype (log-rank: p = 0.03). Cumulative incidence for ischemic stroke was also lower for (-444)CC versus AA genotype (log-rank: p = 0.04). Multifactorially adjusted hazard ratios for TIA were 5.2(95% CI:1.9-14) for (-1072)AA versus GG genotype, and 0.4(0.2-1.0) for (-444)CC versus AA genotype. Corresponding values were 1.9 (0.7-5.2) and 0.7 (0.5-1.0) for ischemic stroke, and 0.8 (0.4-1.6) and 1.0 (0.9-1.2) for IHD. In the case-control study, corresponding multifactorially adjusted odds ratios for IHD/coronary atherosclerosis were 0.5 (0.2-1.3) and 1.2 (1.0-1.5). These genotypes were not associated with risk of asthma or COPD. Leukotriene C4 synthase promoter genotypes influence risk of TIA and ischemic stroke, but not risk of IHD/coronary atherosclerosis, asthma, or COPD.

The potential link between atherosclerosis and the 5-lipoxygenase pathway: investigational agents with new implications for the cardiovascular field

The 5-lipoxygenase pathway is responsible for the production of leukotrienes--inflammatory lipid mediators that have a role in innate immunity, but that can also have pathological effects in inflammatory diseases. Recently, a potential link between leukotriene production and atherosclerosis has been proposed. The expression of leukotriene biosynthetic enzymes and leukotriene receptors has been identified in coronary and carotid atherosclerotic plaques, and the levels of biosynthetic enzymes have been correlated with the clinical symptoms of unstable plaques. Genetic variants in 5-lipoxygenase pathway genes have also been associated with a relative risk of developing myocardial infarction and stroke. On the basis of these discoveries, antileukotriene compounds are now being evaluated for the treatment of cardiovascular disease. Several tool compounds have been shown to limit the progression of lesion development in preclinical models of atherosclerosis, and three compounds, including two drugs previously developed for asthma, are undergoing clinical trials in patients with acute coronary syndromes.

Cysteinyl-leukotrienes and their receptors in asthma and other inflammatory diseases: critical update and emerging trends

Cysteinyl-leukotrienes (cysteinyl-LTs), that is, LTC4, LTD4, and LTE4, trigger contractile and inflammatory responses through the specific interaction with G protein-coupled receptors (GPCRs) belonging to the purine receptor cluster of the rhodopsin family, and identified as CysLT receptors (CysLTRs). Cysteinyl-LTs have a clear role in pathophysiological conditions such as asthma and allergic rhinitis (AR), and have been implicated in other inflammatory conditions including cardiovascular diseases, cancer, atopic dermatitis, and urticaria. Molecular cloning of human CysLT1R and CysLT2R subtypes has confirmed most of the previous pharmacological characterization and identified distinct expression patterns only partially overlapping. Interestingly, recent data provide evidence for the immunomodulation of CysLTR expression, the existence of additional receptor subtypes, and of an intracellular pool of CysLTRs that may have roles different from those of plasma membrane receptors. Furthermore, genetic variants have been identified for the CysLTRs that may interact to confer risk for atopy. Finally, a crosstalk between the cysteinyl-LT and the purine systems is being delineated. This review will summarize and attempt to integrate recent data derived from studies on the molecular pharmacology and pharmacogenetics of CysLTRs, and will consider the therapeutic opportunities arising from the new roles suggested for cysteinyl-LTs and their receptors.

A functional Sp1/Egr1-tandem repeat polymorphism in the 5-lipoxygenase gene is not associated with myocardial infarction

Arachidonate 5-lipoxygenase is an enzyme encoded by the ALOX5 gene, and plays an important role in the synthesis of leukotrienes. These are inflammatory mediators, and have been involved in atherosclerosis and other pathological processes that require proinflammatory activities. Human and animal studies have suggested a role for the ALOX5 gene in atherosclerosis, including a significant association between a promoter polymorphism and a carotid intimal-medial thickness in response to dietary fat. This polymorphism was three- to six-tandem repeats of a Sp1/Egr1 binding motif (GGGCGG)(n), and the number of repeats has been linked with the amount of gene expression. We hypothesized that this ALOX5 polymorphism could influence the risk for myocardial infarction (MI). First, we analysed the effect of the four alleles on gene expression by transfecting the HEK-293 cell line with luciferase reporter-constructs. We found that luciferase activities are dependent on the number of the Sp1/Egr1 repeats, with the three and six repeats having the lowest and highest values. We genotyped 312 male MI survivors, aged < 55 years, and 376 healthy controls matched with patients for sex, age, and ethnicity. Ninety-six per cent of the patients were smokers, compared to only 42% among the controls (P < 0.001; OR = 31.84). The 55 + 56 repeat genotypes were less frequent in patients (55 = 56%, 56 = 0.6%) compared to controls (55 = 60%, 56 = 3%). However, these were non-significantly different frequencies. In addition, no difference in MI-onset age and biochemical values was found between the allele and genotypes. In conclusion, we confirmed the effect of the ALOX5-promoter polymorphism on gene expression, but our data did not support a significant effect of this functional variation on MI risk.