Leukotrienes in atherosclerosis: new target insights and future therapy perspectives

Kounis Syndrome Associated With the Use of Diclofenac

BACKGROUND

Diclofenac is a widely used analgesic, anti-inflammatory, antipyretic drug. In several case reports, its use was associated with the occurrence of Kounis syndrome. The aim of this review was to investigate and summarize published cases of Kounis syndrome suspected to be associated with the use of diclofenac.

METHODS

Electronic searches were conducted in PubMed/MEDLINE, Scopus, Web of Science, Google Scholar, and the Serbian Citation Index.

RESULTS

Twenty publications describing the 20 patients who met inclusion criteria were included in the systematic review. Specified patient ages ranged from 34 to 81 years. Eighteen (90.0%) patients were male. Five patients (25.0%) reported a previous reaction to diclofenac. Reported time from the used dose of diclofenac to onset of the first reaction symptoms ranged from immediately to 5 hours. Diclofenac caused both type I and type II Kounis syndrome, with the presence of various cardiovascular, gastrointestinal, dermatologic, and respiratory signs and symptoms. Most patients experienced hypotension (n = 15 [75.0%]) and chest pain (n = 12 [60.0%]). The most frequently reported finding on electrocardiogram was ST-segment elevations (n = 17 [85.0%]). Coronary angiogram showed normal coronary vessels in 9 patients (45.0%), with some pathologic findings in 8 patients (40.0%).

CONCLUSION

Clinicians should be aware that Kounis syndrome may be an adverse effect of diclofenac. Prompt recognition and withdrawal of the drug, with treatment of both allergic and cardiac symptoms simultaneously, is important.

Clinical significance of polyunsaturated fatty acids in the prevention of cardiovascular diseases

Cardiovascular diseases are one of the most important problems of modern medicine. They are associated with a large number of health care visits, hospitalizations and mortality. Prevention of atherosclerosis is one of the most effective strategies and should start as early as possible. Correction of lipid metabolism disorders is associated with definite clinical successes, both in primary prevention and in the prevention of complications of many cardiovascular diseases. A growing body of evidence suggests a multifaceted role for polyunsaturated fatty acids. They demonstrate a variety of functions in inflammation, both participating directly in a number of cellular processes and acting as a precursor for subsequent biosynthesis of lipid mediators. Extensive clinical data also support the importance of polyunsaturated fatty acids, but all questions have not been answered to date, indicating the need for further research.

Analysis of Clinical Features of Non-steroidal Anti-inflammatory Drugs Induced Kounis Syndrome

Background

Current knowledge of Kounis syndrome induced by non-steroidal anti-inflammatory drugs (NSAIDs) is based on case reports. This study aimed to investigate the clinical features of Kounis syndrome.

Methods

Case reports of the NSAIDs-induced Kounis syndrome were analyzed by searching Chinese and English databases from 1 January 1950 to 31 January 2022.

Results

The median age of the 45 included patients (28 women) was 51 years (20–80 years). NSAIDs that were the most frequently involved were diclofenac (26.7%, 12/45), metamizole (15.6%, 7/45), and aspirin (13.3%, 6/45). Kounis syndrome occurred mainly within 30 min after administration, with a maximum latency of 1 month. Chest pain (75.6%, 34/45), dyspnea (33.3%, 15/45), and allergic reactions (44.4%, 20/45) were the most common clinical manifestations. Thirty patients (66.7%) had an ST-segment elevation on the electrocardiogram. Echocardiogram and coronary angiography showed abnormalities in 21 patients (75%, 21/28) and 15 patients (37.5%, 15/40). Forty-four patients (97.8%) had a good prognosis after treatment with steroids, antihistamines, and vasodilators.

Conclusion

The possibility of Kounis syndrome should be considered in the presence of coronary artery disease symptoms when taking NSAIDs. Kounis syndrome can be life-threatening. It is essential to identify and treat Kounis syndrome correctly.

Molecular Pharmacology of Inflammation Resolution in Atherosclerosis

Atherosclerosis is one of the most important problems of modern medicine as it is the leading cause of hospitalizations, disability, and mortality. The key role in the development and progression of atherosclerosis is the imbalance between the activation of inflammation in the vascular wall and the mechanisms of its control. The resolution of inflammation is the most important physiological mechanism that is impaired in atherosclerosis. The resolution of inflammation has complex, not fully known mechanisms, in which lipid mediators derived from polyunsaturated fatty acids (PUFAs) play an important role. Specialized pro-resolving mediators (SPMs) represent a group of substances that carry out inflammation resolution and may play an important role in the pathogenesis of atherosclerosis. SPMs include lipoxins, resolvins, maresins, and protectins, which are formed from PUFAs and regulate many processes related to the active resolution of inflammation. Given the physiological importance of these substances, studies examining the possibility of pharmacological effects on inflammation resolution are of interest.

Systemic Sclerosis: Elevated Levels of Leukotrienes in Saliva and Plasma Are Associated with Vascular Manifestations and Nailfold Capillaroscopic Abnormalities

The role of leukotrienes (LTs) in the pathogenesis of systemic sclerosis (SSc) needs clarification. We analyzed the association of salivary (sa) and plasma (p) levels (pg/mL) of cysteinyl-leukotrienes (CysLT) and LTB4 with SSc vascular manifestations and nailfold capillaroscopy (NFC) in a cross-sectional study. Patients and healthy controls were evaluated for vascular manifestations and NFC. LTs were compared between groups as follows: SSc with or SSc without vascular features and controls, and by NFC parameters. Twenty SSc patients and 16 volunteers were recruited; Raynaud's phenomenon (RP) history (SSc: saCysLT 99.4 ± 21.8 vs. controls: 23.05 ± 23.7, p = 0.01), RP at examination (SSc: saCysLT 129.3 ± 24.6 vs. controls: 23.05 ± 22.46, p = 0.01; pCysLT SSc: 87.5 ± 11.2 vs. controls: 32.37 ± 10.75, p = 0.002), capillary loss (saCysLT 138.6 ± 26.7 vs. 23.05 ± 21.6, p = 0.0007; saLTB4 3380.9 ± 426.6 vs. 1216.33 ± 346.1, p = 0.0005), "late" scleroderma pattern vs. controls (saCysLT 205.6 ± 32 vs. 23 ± 19.6, p = 0.0002; saLTB4 4564.9 ± 503.6 vs. 1216.3 ± 308.3; p < 0.0001) were all significant. Late patterns had higher levels (saCysLT, p = 0.002; LTB4 p = 0.0006) compared to active and early patterns (LTB4, p = 0.0006), and giant capillaries (p = 0.01) showed higher levels of LTs. Levels of pCysLT were higher in patients with RP at examination vs. patients without RP; saCysLT and LTB4 were higher in SSc group with vs. without capillary loss. LTs could be involved in the pathophysiology of vascular abnormalities. Further research is required to determine if blocking LTs could be a therapeutic target for SSc vascular manifestations.

Molecular and Cellular Mechanisms of Electronegative Lipoproteins in Cardiovascular Diseases

Dysregulation of glucose and lipid metabolism increases plasma levels of lipoproteins and triglycerides, resulting in vascular endothelial damage. Remarkably, the oxidation of lipid and lipoprotein particles generates electronegative lipoproteins that mediate cellular deterioration of atherosclerosis. In this review, we examined the core of atherosclerotic plaque, which is enriched by byproducts of lipid metabolism and lipoproteins, such as oxidized low-density lipoproteins (oxLDL) and electronegative subfraction of LDL (LDL(−)). We also summarized the chemical properties, receptors, and molecular mechanisms of LDL(−). In combination with other well-known markers of inflammation, namely metabolic diseases, we concluded that LDL(−) can be used as a novel prognostic tool for these lipid disorders. In addition, through understanding the underlying pathophysiological molecular routes for endothelial dysfunction and inflammation, we may reassess current therapeutics and might gain a new direction to treat atherosclerotic cardiovascular diseases, mainly targeting LDL(−) clearance.

Extracellular vesicle-associated lipids in central nervous system disorders

Increasing evidence indicates that lipid metabolism is disturbed in central nervous system (CNS) disorders, such as multiple sclerosis, Alzheimer's, and Parkinson's disease. Extracellular vesicles (EVs), including exosomes and microvesicles, are nanosized particles that play an essential role in intercellular communication and tissue homeostasis by transporting diverse biologically active molecules, including a large variety of lipid species. In the last decade, studies defined that changes in the EV lipidome closely correlate with disease-progression and -remission in CNS disorders. In this review, we summarize and discuss these changes in the EV lipidome and elaborate on the impact of different EV-associated lipids on pathological processes in CNS disorders. We conclude that EV-associated lipids are closely associated with neuroinflammation, CNS repair, and pathological protein aggregation in CNS disorders, and that modulation of the EV lipidome represents a promising therapeutic strategy to halt disease progression in multiple sclerosis, Alzheimer's, and Parkinson's disease. Moreover, we predict that disease-stage specific EV-associated lipid signatures can be invaluable markers for the diagnosis and early detection of CNS disorders in the future.

Extracellular vesicles in atherosclerosis

Extracellular vesicles (EVs), which exist in human blood, are increased in some inflammation-related cardiovascular diseases. EVs are involved in inflammation, immunity, signal transduction, cell survival and apoptosis, angiogenesis, thrombosis, and autophagy, all of which are highly significant for maintaining homeostasis and disease progression. Therefore, EVs are also associated with key steps in atherosclerosis, including cellular lipid metabolism, endothelial dysfunction and vascular wall inflammation, ultimately resulting in vascular remodelling. In this review, we summarize recent studies on EV contents and biological function, focusing on their potential effect in atherosclerosis, including cholesterol metabolism, vascular inflammation, angiogenesis, coagulation and the development of atherosclerotic lesions. EVs may represent potential biomarkers and pharmacological targets for atherosclerotic diseases.

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.

BLTR1 in Monocytes Emerges as a Therapeutic Target For Vascular Inflammation With a Subsequent Intimal Hyperplasia in a Murine Wire-Injured Femoral Artery

Given the importance of high-mobility group box 1 (HMGB1) and 5-lipoxygenase (5-LO) signaling in vascular inflammation, we investigated the role of leukotriene signaling in monocytes on monocyte-to-macrophage differentiation (MMD) induced by HMGB1, and on vascular inflammation and subsequent intimal hyperplasia in a mouse model of wire-injured femoral artery. In cultured primary bone marrow-derived cells (BMDCs) stimulated with HMGB1, the number of cells with macrophage-like morphology was markedly increased in association with an increased expression of CD11b/Mac-1, which were attenuated in cells pre-treated with Zileuton, a 5-LO inhibitor as well as in 5-LO-deficient BMDCs. Of various leukotriene receptor inhibitors examined, which included leukotriene B4 receptors (BLTRs) and cysteinyl leukotriene receptors (cysLTRs), the BLTR1 inhibitor (U75302) exclusively suppressed MMD induction by HMGB1. The importance of BLTR1 in HMGB1-induced MMD was also observed in BMDCs isolated from BLTR1-deficient mice and BMDCs transfected with BLTR1 siRNA. Although leukotriene B4 (LTB4) had minimal direct effects on MMD in control and 5-LO-deficient BMDCs, MMD attenuation by HMGB1 in 5-LO-deficient BMDCs was significantly reversed by exogenous LTB4, but not in BLTR1-deficient BMDCs, suggesting that LTB4/BLTR1-mediated priming of monocytes is a prerequisite of HMGB1-induced MMD. In vivo, both macrophage infiltration and intimal hyperplasia in our wire-injured femoral artery were markedly attenuated in BLTR1-deficient mice as compared with wild-type controls, but these effects were reversed in BLTR1-deficient mice transplanted with monocytes from control mice. These results suggest that BLTR1 in monocytes is a pivotal player in MMD with subsequent macrophage infiltration into neointima, leading to vascular remodeling after vascular injury.

Shen-Yuan-Dan Capsule Inhibiting Inflammatory Reaction by Regulating Insulin Receptor Substrate 1/PI3K/Akt/NF-κB Signaling Pathway in Apoliprotein E Knockout Mice Fed with a High-Fat Diet

BACKGROUND

Shen-Yuan-Dan Capsule (SYDC), a traditional Chinese medicine, is proposed to have the capacity to prevent angina pectoris. However, the effects and the related mechanisms of SYDC on atherosclerosis (AS) are still unknown. This study was designed to investigate the effects of SYDC on AS and inflammatory reaction in the apoliprotein E-knockout (ApoE-/-) mice fed with a high-fat diet.

METHODS

Thirty eight-week-old male ApoE-/- mice were randomly divided into three groups (n = 10) 6 weeks after being fed with a high-fat diet: the control group, the lipitor group, and the SYDC group. The hearts were collected for hematoxylin and eosin (HE) or Van Gieson (VG) staining, and the aortas were collected for quantitative reverse transcription polymerase chain reaction (RT-PCR) and western-blotting.

RESULTS

The data showed that the levels of total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL-C), atherosclerotic indexes (AI) and the corrected areas of atherosclerotic plaque of the mice on SYDC group were significantly decreased compared with those of the mice in the control group (p < 0.01, p < 0.05). SYDC can significantly increase collagen proportion in plaques as compared to the untreated mice (p < 0.01). In addition, the messenger ribonucleic acid (mRNA) expressions of insulin receptor substrate 1 (IRS-1), PI3K, Akt, NF-κB and tumor necrosis factor-α (TNF-α) in the mice fed with a high-fat diet were significantly reduced by SYDC (p < 0.05, p < 0.01).

CONCLUSIONS

SYDC can exert an anti-atherosclerotic effect on ApoE-/- mice fed with a high-fat diet. The action mechanism of SYDC was attributed to its ability to inhibit inflammatory reaction by regulating IRS-1/PI3K/Akt/NF-κB signaling pathway.

Meloxicam fails to augment the reno-protective effects of soluble epoxide hydrolase inhibition in streptozotocin-induced diabetic rats via increased 20-HETE levels

The pro-inflammatory cyclooxygenase (COX)-derived prostaglandins and the anti-inflammatory cytochrome P450 epoxygenase-derived epoxyeicosatrienoic acids (EETs) play an important role in the regulation of renal injury. The current study examined whether COX inhibition augments the reno-protective effects of increased EETs levels via inhibiting EETs degradation by soluble epoxide hydrolase (sEH) in diabetic rats. Streptozotocin (50mg/kg, i.v) was used to induce diabetes in male Sprague Dawley rats. Rats were then divided into 5 groups (n=6-8); control non diabetic, diabetic, diabetic treated with the sEH inhibitor trans-4-[4-(3-adamantan-1-yl-ureido)-cyclohexyloxy]-benzoic acid (t-AUCB), diabetic treated with the COX inhibitor meloxicam and diabetic treated with meloxicam plus t-AUCB for 2 months. Glomerular albumin permeability and urinary albumin and nephrin excretion levels were significantly elevated in diabetic rats together with decreased glomerular α3 integrin and nephrin expression levels. Inhibition of sEH reduced glomerular albumin permeability, albumin and nephrin excretion levels and restored the decrease in glomerular α3 integrin and nephrin expression in diabetic rats. Meloxicam failed to reduce renal injury or even to synergize the reno-protective effects of sEH inhibition in diabetic rats. Furthermore, inhibition of sEH reduced the elevation in renal collagen deposition and urinary MCP-1 excretion levels together with a reduction in the number of renal TUNEL positive cells in diabetic vs. control rats (P<0.05). Meloxicam did not reduce renal inflammation or apoptosis in diabetic rats or even exacerbate the anti-inflammatory and anti-apoptotic effects of sEH inhibition. Renal 20-hydroxyeicosatetranoic acid (20-HETE) levels were elevated in diabetic rats and meloxicam further exacerbated this elevation. In conclusion, our study suggests that inhibition of COX failed to provide renal protection or to augment the reno-protective effects of sEH inhibition in diabetic rats, at least in part, via increased inflammatory 20-HETE levels.

Exposure to concentrated ambient fine particulate matter disrupts vascular endothelial cell barrier function via the IL-6/HIF-1α signaling pathway

Exposure to concentrated ambient fine particulate matter (PM2.5) has been associated with cardiovascular diseases (CVDs). The barrier function of vascular endothelial cells is critical for the development of CVDs. Here, we employed human umbilical vein endothelial cells to clarify the function of ambient PM2.5 pollution in the regulation of membrane permeability of vascular endothelial cells. The results show that a high concentration of PM2.5, which mainly includes heavy metals and polycyclic aromatic hydrocarbons, induces barrier dysfunction of vascular endothelial cells. This was mediated in part by promoting IL‐6 expression, which then increases the transcriptional activity of HIF‐1α by promoting its translocation to the nucleus. Our findings indicate that concentrated PM2.5 can destroy membrane integrity and promote permeability in vascular endothelial cells, thereby contributing to the development of CVDs.

Differential Expression of Inflammation-Related Genes in Children with Down Syndrome

OBJECTIVE

The aim of the study was to investigate the expression patterns of a specific set of genes involved in the inflammation process in children with Down Syndrome (DS) and children without the syndrome (control group) to identify differences that may be related to the immune abnormalities observed in DS individuals.

METHOD

RNA samples were obtained from peripheral blood, and gene expression was quantified using the TaqMan® Array Plate Human Inflammation Kit, which facilitated the investigation into 92 inflammation-related genes and four reference genes using real-time polymerase chain reaction (qPCR).

RESULTS

Twenty genes showed differential expression in children with DS; 12 were overexpressed (PLA2G2D, CACNA1D, ALOX12, VCAM1, ICAM1, PLCD1, ADRB1, HTR3A, PDE4C, CASP1, PLA2G5, and PLCB4), and eight were underexpressed (LTA4H, BDKRB1, ADRB2, CD40LG, ITGAM, TNFRSF1B, ITGB1, and TBXAS1). After statistically correcting for the false discovery rate, only the genes BDKRB1 and LTA4H showed differential expression, and both were underexpressed within the DS group.

CONCLUSION

DS children showed differential expression of inflammation-related genes that were not located on chromosome 21 compared with children without DS. The BDKRB1 and LTA4H genes may differentiate the case and control groups based on the inflammatory response, which plays an important role in DS pathogenesis.

Anethole and eugenol reduce in vitro and in vivo leukocyte migration induced by fMLP, LTB4, and carrageenan

The aim of this study was to investigate the effect of anethole (AN) and eugenol (EUG) on leukocyte migration using in vitro chemotaxis and in situ microcirculation assays. BALB/c mice were used for the in vitro chemotaxis assay, and Wistar rats for the in situ microcirculation assay. We evaluated (a) the in vitro leukocyte migration in response to chemotactic factors (formyl-methionyl-leucyl-phenylalanine [fMLP] and leukotriene B4 [LTB4]) and (b) the rolling, adhesion, and migration of leukocytes induced by an injection of carrageenan (100 µg/cavity) into the scrotum of the animal. In the in vitro chemotaxis assay, AN and EUG at doses of 1, 3, 9, and 27 µg/ml significantly inhibited leukocyte migration when stimulated by the chemotactic agents fMLP and LTB4. In the in situ microcirculation assay, AN at doses of 125 and 250 mg/kg and EUG at a dose of 250 mg/kg significantly decreased the number of leukocytes that rolled, adhered, and migrated to perivascular tissue. The results indicate that AN and EUG exert inhibitory effects on leukocyte migration, highlighting their possible use to diminish excessive leukocyte migration in the inflammatory process.

Stress triggers coronary mast cells leading to cardiac events

OBJECTIVE

Stress precipitates and worsens not only asthma and atopic dermatitis but also acute coronary syndromes (ACSs), which are associated with coronary inflammation. Evidence linking stress to ACS was reviewed and indicated that activation of coronary mast cells (MCs) by stress, through corticotropin-releasing hormone (CRH) and other neuropeptides, contributes to coronary inflammation and coronary artery disease.

DATA SOURCES

PubMed was searched (2005-2013) for articles using the following keywords: allergies, anaphylaxis, anxiety, coronary arteries, coronary artery disease, C-reactive protein, cytokines, chymase, histamine, hypersensitivity, interleukin-6 (IL-6), inflammation, mast cells, myocardial ischemia, niacin, platelet-activating factor, rupture, spasm, statins, stress, treatment, tryptase, and uroctortin.

STUDY SELECTIONS

Articles were selected based on their relevance to how stress affects ACS and how it activates coronary MCs, leading to coronary hypersensitivity, inflammation, and coronary artery disease.

RESULTS

Stress can precipitate allergies and ACS. Stress stimulates MCs through the activation of high-affinity surface receptors for CRH, leading to a CRH-dependent increase in serum IL-6. Moreover, neurotensin secreted with CRH from peripheral nerves augments the effect of CRH and stimulates cardiac MCs to release IL-6, which is elevated in ACS and is an independent risk factor for myocardial ischemia. MCs also secrete CRH and uroctortin, which induces IL-6 release from cardiomyocytes. The presence of atherosclerosis increases the risk of cardiac MC activation owing to the stimulatory effect of lipoproteins and adipocytokines. Conditions such as Kounis syndrome, mastocytosis, and myalgic encephalopathy/chronic fatigue syndrome are particularly prone to coronary hypersensitivity reactions.

CONCLUSION

Inhibition of cardiac MCs may be a novel treatment approach.

Genetic ablation of 12/15-lipoxygenase but not 5-lipoxygenase protects against denervation-induced muscle atrophy

Skeletal muscle atrophy is a debilitating outcome of a number of chronic diseases and conditions associated with loss of muscle innervation by motor neurons, such as aging and neurodegenerative diseases. We previously reported that denervation-induced loss of muscle mass is associated with activation of cytosolic phospholipase A2 (cPLA2), the rate-limiting step for the release of arachidonic acid from membrane phospholipids, which then acts as a substrate for metabolic pathways that generate bioactive lipid mediators. In this study, we asked whether 5- and 12/15-lipoxygenase (LO) lipid metabolic pathways downstream of cPLA2 mediate denervation-induced muscle atrophy in mice. Both 5- and 12/15-LO were activated in response to surgical denervation; however, 12/15-LO activity was increased ~2.5-fold versus an ~1.5-fold increase in activity of 5-LO. Genetic and pharmacological inhibition of 12/15-LO (but not 5-LO) significantly protected against denervation-induced muscle atrophy, suggesting a selective role for the 12/15-LO pathway in neurogenic muscle atrophy. The activation of the 12/15-LO pathway (but not 5-LO) during muscle atrophy increased NADPH oxidase activity, protein ubiquitination, and ubiquitin-proteasome-mediated proteolytic degradation. In conclusion, this study reveals a novel pathway for neurogenic muscle atrophy and suggests that 12/15-LO may be a potential therapeutic target in diseases associated with loss of innervation and muscle atrophy.

Functional characterization of genetic enzyme variations in human lipoxygenases

Mammalian lipoxygenases play a role in normal cell development and differentiation but they have also been implicated in the pathogenesis of cardiovascular, hyperproliferative and neurodegenerative diseases. As lipid peroxidizing enzymes they are involved in the regulation of cellular redox homeostasis since they produce lipid hydroperoxides, which serve as an efficient source for free radicals. There are various epidemiological correlation studies relating naturally occurring variations in the six human lipoxygenase genes (SNPs or rare mutations) to the frequency for various diseases in these individuals, but for most of the described variations no functional data are available. Employing a combined bioinformatical and enzymological strategy, which included structural modeling and experimental site-directed mutagenesis, we systematically explored the structural and functional consequences of non-synonymous genetic variations in four different human lipoxygenase genes (ALOX5, ALOX12, ALOX15, and ALOX15B) that have been identified in the human 1000 genome project. Due to a lack of a functional expression system we resigned to analyze the functionality of genetic variations in the hALOX12B and hALOXE3 gene. We found that most of the frequent non-synonymous coding SNPs are located at the enzyme surface and hardly alter the enzyme functionality. In contrast, genetic variations which affect functional important amino acid residues or lead to truncated enzyme variations (nonsense mutations) are usually rare with a global allele frequency<0.1%. This data suggest that there appears to be an evolutionary pressure on the coding regions of the lipoxygenase genes preventing the accumulation of loss-of-function variations in the human population.

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Non-synonymous coding variations in human lipoxygenases are mostly rare with a global allele frequency <1%.

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Common ALOX SNPs are mainly localized on the enzyme surface and hardly effect the enzyme functionality.

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hALOX15B Ala416Asp is a newly discovered loss-of-function mutation in the hALOX gene family while inactivity seems to be caused by severe structural alterations.

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Our data indicate that there is evolutionary pressure on these redox enzymes preventing the accumulation of loss-of-function variations in the human population.

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1000 Genome database is a useful tool to analyze the distribution and functionality of variations in genes of interest.

Activation of TRPV1 prevents OxLDL-induced lipid accumulation and TNF-α-induced inflammation in macrophages: role of liver X receptor α

The transient receptor potential vanilloid type 1 (TRPV1) is crucial in the pathogenesis of atherosclerosis; yet its role and underlying mechanism in the formation of macrophage foam cells remain unclear. Here, we show increased TRPV1 expression in the area of foamy macrophages in atherosclerotic aortas of apolipoprotein E-deficient mice. Exposure of mouse bone-marrow-derived macrophages to oxidized low-density lipoprotein (oxLDL) upregulated the expression of TRPV1. In addition, oxLDL activated TRPV1 and elicited calcium (Ca²⁺) influx, which were abrogated by the pharmacological TRPV1 antagonist capsazepine. Furthermore, oxLDL-induced lipid accumulation in macrophages was ameliorated by TRPV1 agonists but exacerbated by TRPV1 antagonist. Treatment with TRPV1 agonists did not affect the internalization of oxLDL but promoted cholesterol efflux by upregulating the efflux ATP-binding cassette (ABC) transporters ABCA1 and ABCG1. Moreover, the upregulation of ABC transporters was mainly through liver X receptor α- (LXRα-) dependent regulation of transcription. Moreover, the TNF-α-induced inflammatory response was alleviated by TRPV1 agonists but aggravated by the TRPV1 antagonist and LXRα siRNA in macrophages. Our data suggest that LXRα plays a pivotal role in TRPV1-activation-conferred protection against oxLDL-induced lipid accumulation and TNF-α-induced inflammation in macrophages.

Association of Leukotriene Gene Variants and Plasma LTB4 Levels with Coronary Artery Disease in Asian Indians

Leukotrienes are potent inflammatory and lipid mediators that participate in atherosclerosis. We analyzed the association of Leukotriene gene (ALOX5, ALOX5AP, LTA4H, and LTC4S) polymorphisms and plasma Leukotriene B4 (LTB4) levels with coronary artery disease (CAD) in a representative cohort of Asian Indians. In all, 136 functional single nucleotide polymorphisms (SNPs) were selected using in silico tools. Forty-five polymorphic SNPs were ranked for predicted functional effect using FastSNP. Finally, 14 functional SNPs along with 10 SNPs identified from the literature were genotyped in 340 CAD patients and 340 controls. Plasma LTB4 levels were measured in 150 cases and 150 controls. None of the 24 SNPs showed significant association with CAD. Plasma LTB4 levels were higher in cases than in controls (76.42 ± 4.46 pg/mL versus 60.89 ± 2.61 pg/mL) (P=0.003), with greater risk being associated with the top quartile as compared to the bottom quartile after adjusting for potential confounders (OR 8.94, 95% CI 2.56–31.95; P=0.001). Four SNPs in the LTA4H gene showed significant association with LTB4 levels (P<0.05) of which rs1978331 (P=0.035) remained significant after correction for multiple testing. LTB4 showed strong correlation with lipids (r=0.24–34) only in cases. Our pilot study suggests that the association between Leukotrienes gene polymorphisms and CAD risk may be modulated through plasma LTB4 levels.

Coronary hypersensitivity disorder: the Kounis syndrome

BACKGROUND

When allergy or hypersensitivity and anaphylactic or anaphylactoid insults lead to cardiovascular symptoms and signs, including acute coronary events, the result might be the recently defined nosologic entity Kounis syndrome. Vasospastic allergic angina, allergic myocardial infarction, and stent thrombosis with occluding thrombus infiltrated by eosinophils and/or mast cells are the 3 reported variants of this syndrome.

OBJECTIVE

The purpose of this review was to highlight and consolidate the recent literature on allergic angina and allergic myocardial infarction and to propose new therapeutic modalities for stabilizing mast cells.

METHODS

A search for current literature on the pathophysiology, causality, clinical appearance, variance, prevention, and treatment of Kounis syndrome was conducted.

RESULTS

Kounis syndrome is caused by inflammatory mediators such as histamine; neutral proteases, including tryptase, chymase, and cathepsin-D; arachidonic acid products; platelet-activating factor; and a variety of cytokines and chemokines released during the mast-cell activation. Platelets with Fc γ receptor (FcγR) Ι, FcγRII, FcεRI, and FcεRII also have a role in the activation cascade. The same mediators released from the similar inflammatory cells are involved in acute coronary events of nonallergic etiology. These cells are not only present in the involved region before plaque erosion or rupture but also release their contents just before an acute coronary event. Pro-inflammatory mediators similar to those found in Kounis syndrome are found in some cases with nonallergic etiology, suggesting that this is a more general problem. The acute coronary and cerebrovascular events in Kounis syndrome may be prevented by the inhibition of mast-cell degranulation. Substances and natural molecules that protect the mast-cell surface and stabilize the mast-cell membrane are emerging as novel agents in the prevention of acute coronary and other arterial events.

CONCLUSIONS

The 3 reported variants of Kounis syndrome-vasospastic allergic angina, allergic myocardial infarction, and stent thrombosis with occluding thrombus-are caused by inflammatory mediators. Agents that inhibit mast-cell degranulation may be efficacious in preventing the acute coronary and cerebrovascular events of Kounis syndrome.

Adventitial vasa vasorum arteriosclerosis in abdominal aortic aneurysm

Abdominal aortic aneurysm (AAA) is a common disease among elderly individuals. However, the precise pathophysiology of AAA remains unknown. In AAA, an intraluminal thrombus prevents luminal perfusion of oxygen, allowing only the adventitial vaso vasorum (VV) to deliver oxygen and nutrients to the aortic wall. In this study, we examined changes in the adventitial VV wall in AAA to clarify the histopathological mechanisms underlying AAA. We found marked intimal hyperplasia of the adventitial VV in the AAA sac; further, immunohistological studies revealed proliferation of smooth muscle cells, which caused luminal stenosis of the VV. We also found decreased HemeB signals in the aortic wall of the sac as compared with those in the aortic wall of the neck region in AAA. The stenosis of adventitial VV in the AAA sac and the malperfusion of the aortic wall observed in the present study are new aspects of AAA pathology that are expected to enhance our understanding of this disease.

Lipidomic and metabolomic analyses reveal potential plasma biomarkers of early atheromatous plaque formation in hamsters

AIMS

Atherosclerosis is the main pathological process contributing to cardiovascular disease, with diet being the most important factor involved. Although the lipidome of atheromatous plaque has been studied previously, the use of comparative lipidomics and metabolomics in plasma in early atherogenesis could lead to the discovery of plasma biomarkers that allow not only disease prediction but also measurement of disease progression.

METHODS AND RESULTS

High-throughput techniques, such as liquid chromatography/mass spectrometry, allowed us to compare the circulating and aortic lipidome and plasma metabolome in order to look for new molecular targets involved in atherogenesis. To achieve this objective, we chose the hamster (Mesocricetus auratus) as the best small animal model for diet-induced early atherosclerosis, because its lipoprotein metabolism is similar to that of humans. The results revealed the existence of several, previously unreported, changes in lipid and amino-acid metabolism, the peroxisome proliferator-activated receptor γ pathway, and oxidative and endoplasmic reticulum stress, also involving cell senescence. Furthermore, as a proof of concept in the modelling of dietary influences in atherogenesis, we have measured the effect of a potential anti-atherogenic polyphenol extract on the reported pathways. Our results support a previously unknown role for taurocholic acid as a potential plasma biomarker of early atheromatous plaque formation.

CONCLUSION

The use of comparative liquid chromatography/mass spectrometry-based lipidomics and metabolomics allows the discovery of novel pathways in atherogenesis, as well as new potential plasma biomarkers, which could allow us to predict disease in its early stages and measure its progression.

Genetic determinants of 5-lipoxygenase pathway in a Spanish population and their relationship with cardiovascular risk

OBJECTIVE

Leukotrienes (LT) play a role in inflammation, cardiovascular diseases, and cancer. Although some studies suggest that there are genes that determine variability of some LT-related phenotypes, the genetic influence on these phenotypes has not been evaluated.

METHODS

The relative contributions of genetic and environmental influences to the 5-lipoxygenase pathway-related phenotypes (5-Lipoxygenase, five lipoxygenase activating protein (FLAP), LTA(4)-hydrolase and LTC(4)-synthase expression, and LTB(4)-plasma concentration and LTB(4) production by stimulated whole blood) were assessed in a sample of 934 individuals in 35 extended families. Our design is based on extended families recruited through a probands with idiopathic thrombophilia. This strategy allows us the analysis of the effects of measured covariates (such as sex, age and smoking), genes, and environmental variables shared by members of a household.

RESULTS

All of these phenotypes showed significant genetic contributions, with heritabilities ranging from 0.33 to 0.51 for enzyme expression and from 0.25 to 0.50 for LTB(4) production of the residual phenotypic variance. Significant phenotypic and genetic correlation among the LT-related traits was found. More importantly, FLAP and LTA(4)-hydrolase expression exhibit significant genetic correlations with arterial thrombosis, indicating that some of the genes that influence quantitative variation in these phenotypes also influence the risk of thrombosis.

CONCLUSION

This is the first study that quantifies the genetic component of 5-Lipoxygenase pathway phenotypes. The high heritability of these traits and the significant genetic correlations between arterial thrombosis and some of these phenotypes suggest that the exploitation of correlated quantitative phenotypes will aid the search for susceptibility genes.

Association of ALOX5AP haplotypes with susceptibility to coronary artery disease in a Chinese Han population

BACKGROUND

The 5-lipoxygenase activating protein (FLAP), encoded by the activating 5-lipoxygenase (ALOX5AP) gene, is a crucial mediator of the biosynthesis of leukotrienes, which have been implicated in atherosclerosis. This study investigates whether ALOX5AP polymorphisms are associated with coronary artery disease (CAD) in a Chinese Han population.

METHODS

The promoter, exons, splice site region and 3'-untranslated region of the ALOX5AP gene were sequenced in 48 subjects. Three polymorphic sites (-1340T/G, +8733T/C, +20616G/C) found through sequencing were evaluated in 656 patients with angiographically proven CAD and 678 controls with normal coronary angiograms using a polymerase chain reaction and restriction fragment length polymorphism assay. Allelic, genotypic linkage disequilibrium and haplotypic association testing were performed using SHEsis and LDA software. Binary logistic regression was used to control for the presence of vascular risk factors.

RESULTS

Seven single nucleotide polymorphisms (SNPs) were found through screening. No significant differences in allele carriers and genotype frequencies of the ALOX5AP polymorphisms were observed between the two groups. However, when the results of the three SNPs were combined, there was a significant association between two of the haplotypes and the risk of CAD. The haplotype GCG had a significantly greater frequency in patients than in controls (P<0.001, OR=1.728, 95%CI=1.375-2.171), and the frequency of haplotype TCG was higher in controls (P<0.001, OR=0.623, 95%CI=0.519-0.748).

CONCLUSION

The data indicate that ALOX5AP gene variation is a genetic factor associated with interindividual differences in CAD risk.

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.

Kounis syndrome: a new twist on an old disease

Kounis syndrome is the concurrence of acute coronary syndromes with conditions associated with mast cell activation, such as allergies or hypersensitivity and anaphylactic or anaphylactoid insults that can involve other interrelated and interacting inflammatory cells behaving as a 'ball of thread'. It is caused by inflammatory mediators such as neutral proteases including tryptase and chymase, arachidonic acid products, histamine, platelet activating factor and a variety of cytokines and chemokines released during the activation process. Platelets with FCεRI and FCεRII receptors also participate in the above cascade. Vasospastic allergic angina, allergic myocardial infarction and stent thrombosis with occluding thrombus infiltrated by eosinophils and/or mast cells constitute the three reported variants of this syndrome. Kounis syndrome is a ubiquitus disease that represents a magnificent natural paradigm and nature's own experiment, in a final trigger pathway implicated in cases of coronary artery spasm and plaque rupture. Kounis syndrome can complicate anesthesia, vaccination, medical therapy and stent implantation and it seems to be associated with coronary allograft vasculopathy and takotsubo syndrome, it can often be confused with hypersensitivity myocarditis and can be the cause of unexplained sudden death. Kounis syndrome has revealed that the same mediators released from the same inflammatory cells are present in acute coronary events of nonallergic etiology. These cells are not only present in the culprit region before plaque erosion or rupture but they release their contents just before an actual coronary event. Therefore, does Kounis syndrome represent a magnificent natural paradigm and nature's own experiment in a final trigger pathway implicated in cases of coronary artery spasm and plaque rupture showing a novel way towards our effort to prevent acute coronary syndromes? Drugs, substances targeting the stem cell factor that is essential for mast cell development, proliferation, survival, adhesion and homing as well as monoclonal antibodies and natural molecules that protect mast cell surface and stabilize mast cell membrane could emerge as novel therapeutic ways capable to prevent acute coronary and acute cerebrovascular events.

Leukotriene C(4) prevents the complete maturation of murine dendritic cells and modifies interleukin-12/interleukin-23 balance

Leukotriene C(4) is an important mediator in the development of inflammatory reactions and ischaemia. Previous studies have shown that leukotriene C(4) is able to modulate the function of dendritic cells (DCs) and induce their chemotaxis from skin to lymph node. In this study, we decided to evaluate the modulation exerted by leukotriene C(4) on DCs, depending on their status of activation. We showed for the first time that leukotriene C(4) stimulates endocytosis both in immature and lipopolysaccharide (LPS) -activated DCs. Moreover, it suppressed the interleukin-12p70 (IL-12p70) release, but induces the secretion of IL-23 by DCs activated with LPS and promotes the expansion of T helper type 17 (Th17) lymphocytes. Furthermore, blocking the release of IL-23 reduced the percentages of CD4(+) T cells producing IL-17 in a mixed lymphocyte reaction. Ours results suggest that leukotriene C(4) interferes with the complete maturation of inflammatory DCs in terms of phenotype and antigen uptake, while favouring the release of IL-23, the main cytokine involved in the maintenance of the Th17 profile.

Inhibitory effects of ginger (Zingiber officinale Roscoe) essential oil on leukocyte migration in vivo and in vitro

Zingiber officinale Roscoe, popular name ginger, is grown naturally in many parts of the world, including Brazil. Ginger is used in pharmaceutical, cosmetic, and food and beverage industries and the essential oil has been used in folk medicine for manifold conditions including as an analgesic, anti-inflammatory, and antirheumatic. The purpose of this study was to investigate the effects of ginger (Zingiber officinale Roscoe) essential oil (GEO) in an in vitro chemotaxis assay and on leukocyte-endothelial interactions in vivo. GEO was analyzed by GC-MS and the main components identified were ar-curcumene (59%), β-myrcene (14%), 1,8-cineol (8%), citral (7.5%), and zingiberene (7.5%). Oral administration of GEO (200-500 mg/kg) reduced the rolling and leukocyte adherence after 2 h of carrageenan injection (100 μg) into the scrotal chamber. The number of leukocytes migrated to the perivascular tissue 4 h after the irritant stimulus was also diminished. GEO in all doses tested (10(-4), 10(-3), or 10(-2) μL/mL) caused a significant reduction of leukocyte chemotaxis (35.89 ± 4.33, 30.67 ± 0.70, and 35.85 ± 3.83%, respectively) toward casein stimuli. The data presented showed direct and systemic effects of GEO on leukocyte migration as an important mechanism of the anti-inflammatory action of ginger.

Activation of group VI phospholipase A2 isoforms in cardiac endothelial cells

The endothelium comprises a cellular barrier between the circulation and tissues. We have previously shown that activation of protease-activated receptor 1 (PAR-1) and PAR-2 on the surface of human coronary artery endothelial cells by tryptase or thrombin increases group VIA phospholipase A(2) (iPLA(2)β) activity and results in production of multiple phospholipid-derived inflammatory metabolites. We isolated cardiac endothelial cells from hearts of iPLA(2)β-knockout (iPLA(2)β-KO) and wild-type (WT) mice and measured arachidonic acid (AA), prostaglandin I(2) (PGI(2)), and platelet-activating factor (PAF) production in response to PAR stimulation. Thrombin (0.1 IU/ml) or tryptase (20 ng/ml) stimulation of WT endothelial cells rapidly increased AA and PGI(2) release and increased PAF production. Selective inhibition of iPLA(2)β with (S)-bromoenol lactone (5 μM, 10 min) completely inhibited thrombin- and tryptase-stimulated responses. Thrombin or tryptase stimulation of iPLA(2)β-KO endothelial cells did not result in significant PAF production and inhibited AA and PGI(2) release. Stimulation of cardiac endothelial cells from group VIB (iPLA(2)γ)-KO mice increased PAF production to levels similar to those of WT cells but significantly attenuated PGI(2) release. These results indicate that cardiac endothelial cell PAF production is dependent on iPLA(2)β activation and that both iPLA(2)β and iPLA(2)γ may be involved in PGI(2) release.