Complement factor H Y402H gene polymorphism in coronary artery disease and atherosclerosis

Understanding AMD by analogy: systematic review of lipid-related common pathogenic mechanisms in AMD, AD, AS and GN

RATIONALE

Age-related macular degeneration (AMD) is one of the leading causes of blindness among the elderly. Due to its complex etiology, current treatments have been insufficient. Previous studies reveal three systems closely involved in AMD pathogenesis: lipid metabolism, oxidation and inflammation. These systems are also involved in Alzheimer's disease, atherosclerosis and glomerulonephritis. Understanding commonalities of these four diseases may provide insight into AMD etiology.

OBJECTIVES

To understand AMD pathogenesis by analogy and suggest ideas for future research, this study summarizes main commonalities in disease pathogenesis of AMD, Alzheimer's disease, atherosclerosis and glomerulonephritis.

METHODS

Articles were identified through PubMed, Ovid Medline and Google Scholar. We summarized the common findings and synthesized critical differences.

RESULTS

Oxidation, lipid deposition, complement activation, and macrophage recruitment are involved in all four diseases shown by genetic, molecular, animal and human studies. Shared genetic variations further strengthen their connection. Potential areas for future research are suggested throughout the review.

CONCLUSIONS

The four diseases share many steps of an overall framework of pathogenesis. Various oxidative sources cause oxidative stress. Oxidized lipids and related molecules accumulate and lead to complement activation, macrophage recruitment and pathology. Investigations that arise under this structure may aid us to better understand AMD pathology.

Identification of susceptibility modules for coronary artery disease using a genome wide integrated network analysis

Although recent genome-wide association studies (GWAS) have identified a handful of variants with best significance for coronary artery disease (CAD), it remains a challenge to summarize the underlying biological information from the abundant genotyping data. Here, we propose an integrated network analysis that effectively combines GWAS genotyping dataset, protein-protein interaction (PPI) database, literature and pathway annotation information. This three-step approach was illustrated for a comprehensive network analysis of CAD as the following. First, a network was constructed from PPI database and CAD seed genes mined from the available literatures. Then, susceptibility network modules were captured from the results of gene-based association tests. Finally, susceptibility modules were annotated with potential mechanisms for CAD via the KEGG pathway database. Our network analysis identified four susceptibility modules for CAD including a complex module that consisted of 15 functional inter-connected sub-modules, AGPAT3-AGPAT4-PPAP2B module, ITGA11-ITGB1 module and EMCN-SELL module. MAPK10 and COL4A2 among the top-scored focal adhesion pathway related module were the most significant genes (MAPK10: OR=32.5, P=3.5 × 10(-11); COL4A2: OR=2.7, P=2.8 × 10(-10)). The significance of the two genes were further validated by other two gene-based association tests (MAPK10: P=0.009 and 0.007; COL4A2: P=0.001 and 0.023) and another independent GWAS dataset (MAPK10: P=0.001; COL4A2: P=0.0004). Furthermore, 34 out of 44 previously reported CAD susceptibility genes were captured by our CAD PPI network and 17 of them were also significant genes. The susceptibility modules identified in our study might provide novel clues for the clarification of CAD pathogenesis in the future.

The innate immune response to products of phospholipid peroxidation

Lipid peroxidation occurs in the context of many physiological processes but is greatly increased in various pathological situations. A consequence of phospholipid peroxidation is the generation of oxidation-specific epitopes, such as phosphocholine of oxidized phospholipids and malondialdehyde, which form neo-self determinants on dying cells and oxidized low-density lipoproteins. In this review we discuss evidence demonstrating that pattern recognition receptors of the innate immune system recognize oxidation-specific epitopes as endogenous damage-associated molecular patterns, allowing the host to identify dangerous biological waste. Oxidation-specific epitopes are important targets of both cellular and soluble pattern recognition receptors, including toll-like and scavenger receptors, C-reactive protein, complement factor H, and innate natural IgM antibodies. This recognition allows the innate immune system to mediate important physiological house keeping functions, for example by promoting the removal of dying cells and oxidized molecules. Once this system is malfunctional or overwhelmed the development of diseases, such as atherosclerosis and age-related macular degeneration is favored. Understanding the molecular components and mechanisms involved in this process, will help the identification of individuals with increased risk of developing chronic inflammation, and indicate novel points for therapeutic intervention. This article is part of a Special Issue entitled: Oxidized phospholipids—their properties and interactions with proteins.

Genetic variation in complement factor H and risk of coronary heart disease: eight new studies and a meta-analysis of around 48,000 individuals

OBJECTIVES

To investigate the association of polymorphisms in complement factor H (CFH) and coronary heart disease (CHD) using meta-analysis.

BACKGROUND

Age-related macular degeneration (AMD) and CHD may share partially overlapping pathogenesis. A non-synonymous SNP (rs1061170/Y402H) in CFH encoding complement factor H (fH) is robustly associated with increased AMD risk but associations with CHD risk have been inconsistent.

METHODS

We conducted de novo genotyping and genetic association analyses of incident and prevalent CHD in four studies, and in silico analysis of the same association in a further four cohorts. We pooled these data with information from all published studies using random effects meta-analysis, including a total of 48,646 participants of which 9097 were CHD cases. We also evaluated the association of Y402H with known risk factors for CHD by pooling results from new and in silico studies providing relevant data.

RESULTS

CFH genotype was not associated with CHD. Compared to the reference TT homozygote group the pooled odds ratio (OR) for individuals homozygous for the C allele was 1.02, 95% CI (0.91, 1.13) and that for heterozygote TC individuals was 1.04 (0.98, 1.10). There was no association of CFH with systolic and diastolic blood pressure, total-, LDL- and HDL-cholesterol, or body mass index. Individuals who were CC compared to TT had higher triglyceride levels: pooled mean difference 0.06 (0.02, 0.10) mmol/L, p=0.005.

CONCLUSIONS

The AMD-associated CFH genotype is not associated with CHD. With the possible exception of triglycerides, this CFH SNP was not associated with a wide range of other CHD risk factors.

Complement factor H variant Y402H is not a risk factor for preeclampsia in the Finnish population

OBJECTIVE

Variations in complement factor H, which down-regulates the activity of the alternative complement pathway, have been associated with different vascular disorders. Here we examine whether factor H variation is involved in the etiology of preeclampsia.

METHODS

We studied 110 women with preeclampsia and 99 controls for complement factor H variations by sequencing.

RESULTS

No significant differences in the genotype or allele frequencies of the Y402H variant were detected between the two groups. No sequence variations were detected in the short consensus repeat domain 20 of the gene.

CONCLUSIONS

Neither the Y402H variant, nor mutations in the short consensus repeat domain 20 of the gene is associated with preeclampsia. For examination of possible links to other polymorphisms or detection of small genotypic effects, studies in larger sample sets are warranted.

The role of complement in atherosclerosis

PURPOSE OF REVIEW

Although it has long been recognized that atherosclerotic lesions show evidence of complement activation, the functional roles of the complement system in atherogenesis are not yet fully resolved. This article highlights recent publications on the complement system in the atherosclerosis field.

RECENT FINDINGS

There have been a number of recent papers reporting on the association of complement proteins and complement regulators with high density lipoproteins, complement activation by enzymatically-modified LDL, signalling pathways downstream of C3a and C5a receptors and membrane C5b-9 assembly, and the prevention of C5b-9 assembly on endothelial cells via upregulation of CD59 expression in response to arterial laminar flow. C1q has been found to play a protective role in early lesion formation in LDL receptor deficient mice, and Crry-Ig and soluble C1 inhibitor have both been shown to have therapeutic effects in models of vascular injury in ApoE deficient mice. The possibility that the Y402H Factor H polymorphism influences atherosclerosis has been supported in a recent paper showing increased risk in white hypertensive individuals.

SUMMARY

The articles that have emerged over the last year highlight the relevance of the complement system to the atherosclerosis field.

Association of the complement factor H Y402H polymorphism with cardiovascular disease is dependent upon hypertension status: The ARIC study

BACKGROUND

Complement factor H (CFH) is a plasma protein that is essential in the regulation of the alternative complement pathway and has been implicated as taking part in complement inhibition in atherogenesis. We evaluated the association of the Y402H polymorphism with incident coronary heart disease (CHD), incident ischemic stroke, and carotid artery wall thickness (intima-media thickness (IMT)) in the Atherosclerosis Risk in Communities (ARIC) cohort.

METHODS

Incident ischemic stroke and CHD were identified through annual telephone calls and hospital and death certificate surveillance. Carotid IMT was measured by means of high-resolution B-mode ultrasound. Four hundred eighty-three validated ischemic stroke and 1,544 CHD events were identified. Because of allele frequency differences between whites and African Americans, analyses were performed separately according to the racial group.

RESULTS

The 402HH homozygous genotype was a significant predictor of incident ischemic stroke in whites (hazard rate ratio (HRR) 1.47, 95% confidence interval (CI) 1.05-2.05). Significant interaction effects between genotype and hypertension were observed for CHD in whites and for cIMT in whites and African Americans. In further analyses of incident CHD, genotypes carrying the 402H allele were a significant predictor of incident CHD in whites who had hypertension (402YH: HRR 1.19, 95% CI 1.01-1.40; 402HH: HRR 1.28, 95% CI 1.04-1.57). The 402H allele was also associated with higher cIMT measures for whites in the overall cohort, and for whites with hypertension.

CONCLUSION

The CFH 402H allele was associated with an increased risk for incident CHD and ischemic stroke in whites, with the strength and significance of the association dependent upon hypertension status.

Complement Factor H polymorphism Y402H associates with inflammation, visual acuity, and cardiovascular mortality in the elderly population at large

The haplotype tagging Y402H polymorphism in the Complement Factor H gene (CFH) has consistently been associated with age-related macular degeneration, whereas conflicting results have been reported on its relationship with cardiovascular disease. CFH plays a role in inflammation, which is causal to both diseases and both are highly prevalent in old age. Therefore, we investigated whether or not Y402H associated with inflammation, visual acuity, and cardiovascular disease in old age. Within the Leiden 85-plus Study, a prospective population-based study of participants aged 85 years and older, we found that carriers of the CFH 402HH variant had a higher production of IL-6 in whole blood samples compared to those carrying the 402YY variant (P=0.029). Carriers of the 402HH genotype also had a steeper increase in circulating C-reactive protein levels during follow-up (P=0.009), lower visual acuity (P=0.020), and an increased risk of cardiovascular mortality (P=0.004). Subjects in the lowest tertile of visual acuity had a twofold increased risk of cardiovascular mortality compared to those in the highest tertile (P=0.001). We conclude that the CFH Y402H polymorphism associates with inflammation, visual impairment, and cardiovascular mortality in the elderly population at large. Visual impairment identifies elderly with an increased risk of cardiovascular disease.

Genetic variants of complement factor H gene are not associated with premature coronary heart disease: a family-based study in the Irish population

BACKGROUND

The complement factor H (CFH) gene has been recently confirmed to play an essential role in the development of age-related macular degeneration (AMD). There are conflicting reports of its role in coronary heart disease. This study was designed to investigate if, using a family-based approach, there was an association between genetic variants of the CFH gene and risk of early-onset coronary heart disease.

METHODS

We evaluated 6 SNPs and 5 common haplotypes in the CFH gene amongst 1494 individuals in 580 Irish families with at least one member prematurely affected with coronary heart disease. Genotypes were determined by multiplex SNaPshot technology.

RESULTS

Using the TDT/S-TDT test, we did not find an association between any of the individual SNPs or any of the 5 haplotypes and early-onset coronary heart disease.

CONCLUSION

In this family-based study, we found no association between the CFH gene and early-onset coronary heart disease.

Lack of association between complement factor H polymorphisms and coronary artery disease or myocardial infarction

Complement factor H (CFH) plays a critical role in the protection of host cells and tissues from damage by complement activation and has been suggested to protect against the progression of atherosclerosis. A polymorphism in the CFH gene, Y402H, known to be strongly associated with age-related macular degeneration, has been analyzed in relation to coronary artery disease (CAD) in several studies with conflicting results. We investigated the association of polymorphisms of the CFH gene in two large-scale studies on CAD and myocardial infarction (MI). The AtheroGene Study included a cohort of cases with CAD (n = 1,303) prospectively followed for a median period of 6.2 years, among whom198 experienced a cardiovascular event, and a group of 483 control subjects. The AtheroGene Study population was genotyped for the Y402H, I62V, and E936D polymorphisms. There was no significant difference in genotypic or allelic frequencies between CAD cases and controls. Among cases, no significant association was found with prospective cardiovascular outcome. Many inflammatory proteins, including the C-reactive protein, were measured, and none of the polymorphisms showed an association with these markers. The Etude Cas-Témoin de l'Infarctus du Myocarde (ECTIM) Study compared 1,034 patients with MI and 1,039 controls from France and United Kingdom. The ECTIM Study population was genotyped for the Y402H polymorphism. Genotype and allele frequencies were similar in cases and controls. These results do not support an involvement of common nonsynonymous polymorphisms of the CFH gene in predisposition to CAD and its complications.