Promotor polymorphisms in leukotriene C4 synthase and risk of ischemic cerebrovascular disease

Cysteinyl Leukotrienes as Potential Pharmacological Targets for Cerebral Diseases

Cysteinyl leukotrienes (CysLTs) are potent lipid mediators widely known for their actions in asthma and in allergic rhinitis. Accumulating data highlights their involvement in a broader range of inflammation-associated diseases such as cancer, atopic dermatitis, rheumatoid arthritis, and cardiovascular diseases. The reported elevated levels of CysLTs in acute and chronic brain lesions, the association between the genetic polymorphisms in the LTs biosynthesis pathways and the risk of cerebral pathological events, and the evidence from animal models link also CysLTs and brain diseases. This review will give an overview of how far research has gone into the evaluation of the role of CysLTs in the most prevalent neurodegenerative disorders (ischemia, Alzheimer's and Parkinson's diseases, multiple sclerosis/experimental autoimmune encephalomyelitis, and epilepsy) in order to understand the underlying mechanism by which they might be central in the disease progression.

Filaggrin loss-of-function mutations as risk factors for ischemic stroke in the general population

Essentials FLG mutations cause atopic dermatitis, previously found to be associated with ischemic stroke. Association between FLG mutations and ischemic stroke was examined in 97 174 Danish individuals. FLG mutations were associated with increased ischemic stroke risk in the general population. The association was most pronounced in younger individuals, and in current and former smokers.

SUMMARY

Background Heritability studies have shown a considerable genetic component to ischemic stroke risk; however, much is unknown as to which genes are responsible. Also, previous studies have found an association between atopic dermatitis and increased ischemic stroke risk. Objective To test the hypothesis that FLG loss-of-function mutations, known to be associated with atopic dermatitis, were also associated with ischemic stroke. Methods A total of 97 174 individuals, with 3597 cases of ischemic stroke, from the Copenhagen General Population Study, the Copenhagen City Heart Study and the Copenhagen Carotid Stroke Study were genotyped for the two most common filaggrin mutations, FLG R501X and FLG 2282del4. Results FLG mutation carriers had an odds ratio for ischemic stroke of 1.15 (95% confidence interval [CI], 1.02-1.30) compared with non-carriers. Risk of ischemic stroke for FLG mutation carriers was higher among individuals aged < 50 years, with an odds ratio of 1.72 (1.11-2.67), compared with non-carriers. When stratified for smoking, ischemic stroke risk was primarily seen in current and former smokers, with an odds ratio of 1.25 (1.08-1.44). FLG mutations were not associated with conventional cardiovascular risk factors except for slightly more pack-years smoked among mutation carriers, but were associated with increased risk of self-reported eczema, with an odds ratio of 1.42 (1.32-1.52). Finally, self-reported eczema was associated with increased ischemic stroke risk, with an age and sex adjusted hazard ratio of 1.24 (1.01-1.52); however, the association was not statistically significant after multifactorial adjustment. Conclusion In this study of 97 174 individuals from the Danish general population, FLG loss-of-function mutations were associated with increased ischemic stroke risk; however, residual confounding is a possibility.

Common Polymorphisms in the 5-Lipoxygenase Pathway and Risk of Incident Myocardial Infarction: A Danish Case-Cohort Study

BACKGROUND

The 5-lipoxygenase pathway (5-LOX) has been implicated in the development of cardiovascular disease and studies have suggested that genetic polymorphisms related to key enzymes in this pathway may confer risk of myocardial infarction (MI). This study investigated the association of pre-selected genetic polymorphisms in four candidate genes of 5-LOX (arachidonate 5-lipoxygenase and its activating protein (ALOX-5 and FLAP), leukotriene A4 hydroxylase (LTA4-H) and leukotriene C4 synthase (LTC4-S)) with incident MI.

METHODS

In a Danish cohort including 57,053 participants, aged 50-64 at enrolment and recruited from 1993-97, we conducted a case-cohort study including cases with incident MI and a randomly selected sub cohort of 3,000 participants. Cases were identified from national registries through July 2013. A total of 22 SNPs were selected and genotyped using the commercially available KASP™ assay. A tandem-repeat polymorphism, located in the ALOX-5 gene, was genotyped by multi-titre plate sequencing. Haplotypes were inferred using PHASE 2.1.

RESULTS

During a median follow-up of 17.0 years we identified 3,089 cases of incident MI. In FLAP, two SNPs were negatively associated with incident MI (rs9551963 & rs17222842) while one SNP (rs2247570) located in LTA4-H, was associated with higher risk of MI when comparing subjects with two copies of the variant allele to homozygotes for the wild type. However, only rs17222842 remained significantly associated with MI after correcting for multiple testing. Furthermore, the promoter polymorphism rs59439148 was associated with risk of MI in men. For male carriers of two variant alleles we found a hazard ratio of 1.63 (95% CI: 1.06;2.52) compared to homozygotes for the wild type. Previously described haplotypes (Hap-A -B, -E and -K) were not associated with MI in our population.

CONCLUSION

In conclusion, some common polymorphisms in the 5-lipoxygenase pathway were modestly associated with incident MI, suggesting a potential role for this pathway in the development of cardiovascular disease.

Leukotriene-C4 synthase, a critical enzyme in the activation of store-independent Orai1/Orai3 channels, is required for neointimal hyperplasia

Leukotriene-C4 synthase (LTC4S) generates LTC4 from arachidonic acid metabolism. LTC4 is a proinflammatory factor that acts on plasma membrane cysteinyl leukotriene receptors. Recently, however, we showed that LTC4 was also a cytosolic second messenger that activated store-independent LTC4-regulated Ca(2+) (LRC) channels encoded by Orai1/Orai3 heteromultimers in vascular smooth muscle cells (VSMCs). We showed that Orai3 and LRC currents were up-regulated in medial and neointimal VSMCs after vascular injury and that Orai3 knockdown inhibited LRC currents and neointimal hyperplasia. However, the role of LTC4S in neointima formation remains unknown. Here we show that LTC4S knockdown inhibited LRC currents in VSMCs. We performed in vivo experiments where rat left carotid arteries were injured using balloon angioplasty to cause neointimal hyperplasia. Neointima formation was associated with up-regulation of LTC4S protein expression in VSMCs. Inhibition of LTC4S expression in injured carotids by lentiviral particles encoding shRNA inhibited neointima formation and inward and outward vessel remodeling. LRC current activation did not cause nuclear factor for activated T cells (NFAT) nuclear translocation in VSMCs. Surprisingly, knockdown of either LTC4S or Orai3 yielded more robust and sustained Akt1 and Akt2 phosphorylation on Ser-473/Ser-474 upon serum stimulation. LTC4S and Orai3 knockdown inhibited VSMC migration in vitro with no effect on proliferation. Akt activity was suppressed in neointimal and medial VSMCs from injured vessels at 2 weeks postinjury but was restored when the up-regulation of either LTC4S or Orai3 was prevented by shRNA. We conclude that LTC4S and Orai3 altered Akt signaling to promote VSMC migration and neointima formation.

Association of ALOX5, LTA4H and LTC4S gene polymorphisms with ischemic stroke risk in a cohort of Chinese in east China

BACKGROUND

Genetic variations of the 5-lipoxygenase activating protein and leukotriene A4 hydrolase genes that confer an increased risk of ischemic stroke have implicated the family of leukotrienes as potential mediators of ischemic stroke. This study aimed to explore the association of ALOX5, LTA4H and LTC4S gene polymorphisms with ischemic stroke risk in a cohort of Chinese in east China.

METHODS

This case-control study consisted of 690 patients with ischemic stroke and 690 controls. Polymorphisms of ALOX5 rs2029253 A/G, LTA4H rs6538697 T/C, and LTC4S rs730012 A/C were genotyped by the polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP) analysis. The multivariate logistic regression model was used to exclude the effects of conventional risk factors on ischemic stroke.

RESULTS

Carriers of C allele in rs730012 were more susceptible to ischemic stroke (OR: 1.37; 95%CI: 1.08-1.73; P=0.009). The rs2029253 GG genotype showed a risk-reducing effect on ischemic stroke (OR: 0.72; 95%CI: 0.55-0.93; P=0.013) while the rs6538697 CC genotype had an increased risk of ischemic stroke (OR: 1.77; 95%CI: 1.09-2.89; P=0.022). The rs730012 variant was not associated with ischemic stroke risk after adjusting confounding factors (P>0.05).

CONCLUSION

The present study suggested that gene polymorphisms in the leukotrienes pathway may exert influences, with independent genetic effects, on ischemic stroke susceptibility in a cohort of Chinese in east China.

Elevated levels of leukotriene B4 and thromboxane B2 distinguish chest pain of cardiac and non cardiac origin

OBJECTIVE

Myocardial infarction (MI) is often preceded by severe chest pain. The use of inflammatory markers to distinguish between chest pain of cardiac and non cardiac origin are not well reported. The aim of the study was to distinguish the chest pain of non cardiac and cardiac origin by using reliable inflammatory markers.

METHODS

The present study enrolled 80 subjects including chest pain which lead to myocardial infarction (n=40), non-cardiac chest pain (CP) patients (n=20) and healthy volunteers (N) (n=20). Leukotriene B4 (LTB4) and thromboxane B2 (TXB2) levels were analyzed along with hs-CRP.

RESULTS

Receiver operating characteristic (ROC) curve analysis showed LTB4 and TXB2 to be a good discriminator between patients with chest pain of cardiac and non cardiac in origin. The area under the curve was found to be 0.988 and 0.925 for LTB4 and TXB2, respectively when compared with hs-CRP. The sensitivity and specificity of LTB4 and TXB2 were found to be 90, 85% and 95, 90%, respectively.

CONCLUSION

The measurement of LTB4 and TXB2 levels may therefore be useful to distinguish the chest pain leading to MI from that of non cardiac in origin and for the management of the disease.

Genetic variation in members of the leukotrienes biosynthesis pathway confers risk of ischemic stroke in Eastern Han Chinese

This study was aimed to explore the association of genetic variation in members of the leukotrienes biosynthesis pathway as potential mediators with ischemic stroke (IS) risk in Eastern Han Chinese. A case-control study of was conducted with five selected single nucleotide polymorphisms (SNPs). In the single-locus analysis, carriers of C allele of rs730012 in LTC4S were more susceptible to IS (OR, 1.28; 95% CI, 1.02-1.60; P=0.033). Under the recessive genetic model, ALOX5 rs2029253 variant reduced IS risk (adjusted OR, 0.78; 95% CI, 0.60-1.00; P=0.048) while LTA4H rs6538697 and LTC4S rs730012 variants increased (adjusted OR, 1.66; 95% CI, 1.04-2.64; P=0.032 and adjusted OR, 3.63; 95% CI, 1.01-13.05; P=0.048, respectively). However, there was no evidence of association between all five SNPs and IS risk after correction for multiple testing. In combined analysis of multiple genes and loci, individuals with ALOX5AP rs12429692 T allele, ALOX5 rs2029253 A allele, and LTA4H rs6538697 C allele suggested a significantly increased susceptibility to IS (adjusted OR, 1.70; 95% CI, 1.07-2.69; P=0.024). The present study suggested gene-gene interactions in leukotrienes pathway could exert influences on the risk of IS.

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 PLA2G4A with myocardial infarction is modulated by dietary PUFAs

BACKGROUND

Leukotrienes are proinflammatory molecules derived from dietary PUFAs and have been associated with cardiovascular disease (CVD). We previously reported that an A→G variant (rs12746200) of the cytosolic phospholipase A2 group IVA gene (PLA2G4A), which encodes the enzyme that liberates PUFAs from cellular membranes for leukotriene synthesis, decreases the risk of CVD.

OBJECTIVE

We sought to replicate these initial observations with a more clinically relevant phenotype, such as myocardial infarction (MI), and to determine whether dietary PUFAs mediate this association.

DESIGN

In a Costa Rican case-control data set (n = 3971), rs12746200 was genotyped and was tested for an association with MI. Functional experiments were carried out to determine whether rs12746200 led to differences in mRNA expression.

RESULTS

Risk of MI was significantly lower in AG/GG subjects than in AA homozygotes (OR: 0.86; 95% CI: 0.75, 0.99; P = 0.040). The reduced risk of MI was observed primarily in AG/GG subjects who were above the median for intake of dietary omega-6 (n-6) PUFAs (OR: 0.71; 95% CI: 0.59, 0.87; P-interaction = 0.005). A similar analysis with dietary omega-3 (n-3) PUFAs did not show a statistically significant nutrigenetic association (P-interaction = 0.23). Functional analysis in human aortic endothelial cells showed that the carriers of the G allele had significantly lower PLA2G4A gene expression (P = 0.014), consistent with the atheroprotective association of this variant.

CONCLUSION

These results replicate the association of rs12746200 with CVD phenotypes and provide evidence that the protective association of this functional PLA2G4A variant is mediated by dietary PUFAs.

Genetics of stroke

Stroke is the second most common cause of death and the most common cause of disability in developed countries. Stroke is a multi-factorial disease caused by a combination of environmental and genetic factors. Numerous epidemiologic studies have documented a significant genetic component in the occurrence of strokes. Genes encoding products involved in lipid metabolism, thrombosis, and inflammation are believed to be potential genetic factors for stroke. Although a large group of candidate genes have been studied, most of the epidemiological results are conflicting. Studies of stroke as a monogenic disease have made huge progress, and animal models serve as an indispensable tool to dissect the complex genetics of stroke. In the present review, we provide insight into the role of in vivo stroke models for the study of stroke genetics.

Novel mutations in leukotriene C4 synthase and risk of cardiovascular disease based on genotypes from 50,000 individuals

BACKGROUND

Atherosclerosis is an inflammatory condition where cysteinyl leukotrienes have been identified to play an important role. Furthermore, cysteinyl leukotrienes may also affect thrombus formation. Using prospective, cross-sectional and case-control designs, we tested the hypothesis that hitherto unknown genetic variation, likely to affect the function of leukotriene C(4) synthase, is associated with risk of venous thromboembolism, ischemic stroke and myocardial infarction.

METHODS AND RESULTS

Resequencing the gene coding for leukotriene C(4) synthase in an extreme risk population with more than 1500 individuals revealed 17 new mutations, of which four are likely to change protein function (211G>A (minor allele frequency, 0.0001), IVS3 + 1G>A (0.002), 374G>A (0.0006) and 451_453+10del (0.0007)). Based on genotyping 50,000 individuals, age and sex adjusted odds ratios for venous thromboembolism were 2.0 (95% CI, 1.3-3.5) for IVS3+1G>A heterozygotes vs. wild type, and 1.9 (1.5-2.7) for any mutation heterozygote vs. wild type. Corresponding values were 2.0 (1.3-3.2) and 1.5 (1.1-2.1) for ischemic stroke, and 1.0 (0.8-1.3) and 1.2 (1.0-1.4) for myocardial infarction.

CONCLUSIONS

Four novel mutations that are likely to change the function of leukotriene C(4) synthase were associated with increased risk of venous thromboembolism and ischemic stroke. These findings need confirmation in other independent studies. In addition, the mechanism behind these findings deserves further investigation.

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.

Leukotriene signaling in atherosclerosis and ischemia

INTRODUCTION

The inflammatory process of atherosclerosis is associated with several pathophysiological reactions within the vascular wall. The arachidonic acid released by phospholipase A(2) serves as substrate for the production of a group of lipid mediators known as the leukotrienes, which induce pro-inflammatory signaling through activation of specific BLT and CysLT receptors.

DISCUSSION

Leukotriene signaling has been implicated in early lipid retention and foam cell accumulation, as well as in the development of intimal hyperplasia and advanced atherosclerotic lesions. Furthermore, the association of leukotrienes with degradation of extracellular matrix has suggested a role in atherosclerotic plaque rupture. Finally, studies of either myocardial or cerebral ischemia and reperfusion indicate that leukotriene signaling in addition may be involved in the development of ischemic injury.

CONCLUSION

Both leukotriene synthesis inhibitors and leukotriene receptor antagonists have been suggested to induce beneficial effects at different stages of the atherosclerosis process.