Association of a common TLR-6 polymorphism with coronary artery disease - implications for healthy ageing?

BACKGROUND: The pro-inflammatory status of the elderly triggers most of the age-related diseases such as cancer and atherosclerosis. Atherosclerosis, the leading cause world wide of morbidity and death, is an inflammatory disease influenced by life-style and genetic host factors. Stimuli such as oxLDL or microbial ligands have been proposed to trigger inflammation leading to atherosclerosis. It has recently been shown that oxLDL activates immune cells via the Toll-like receptor (TLR) 4/6 complex. Several common single nucleotide polymorphisms (SNPs) of the TLR system have been associated with atherosclerosis. To investigate the role of TLR-6 we analyzed the association of the TLR-6 SNP Pro249Ser with atherogenesis. RESULTS: Genotyping of two independent groups with CAD, as well as of healthy controls revealed a significant association of the homozygous genotype with a reduced risk for atherosclerosis (odds ratio: 0.69, 95% CI 0.51-0.95, P = 0.02). In addition, we found a trend towards an association with the risk of restenosis after transluminal coronary angioplasty (odds ratio: 0.53, 95% CI 0.24-1.16, P = 0.12). In addition, first evidence is presented that the frequency of this protective genotype increases in a healthy population with age. Taken together, our results define a role for TLR-6 and its genetic variations in modulating the inflammatory response leading to atherosclerosis. CONCLUSIONS: These results may lead to a better risk stratification, and potentially to an improved prophylactic treatment of high-risk populations. Furthermore, the protective effect of this polymorphism may lead to an increase of this genotype in the healthy elderly and may therefore be a novel genetic marker for the well-being during aging.

Toll-like receptor (TLR)-9 promotor polymorphisms and atherosclerosis.

BACKGROUND: Currently, the primary cause of atherosclerosis remains controversial: while oxidized or enzymatically altered LDL is widely accepted as one cause of the inflamed lesion, microorganisms such as C. pneumoniae or cytomegalovirus (CMV) also have recently been postulated to be involved in the pathogenesis of atherosclerosis. Microbial products activate innate immune cells of the host via Toll-like receptors (TLRs). Common polymorphisms of the TLR-2 and TLR-4 genes have been shown to be associated with an increased risk for restenosis after PTCA, and a lower risk of carotid atherosclerosis, respectively. Microbial DNA has been shown to activate immune cells via the cytosolic TLR-9. Specially, C. pneumonia and CMV as intracellular pathogens may be potent trigger of TLR-9 signaling. Therefore, we investigated whether the two common promotor polymorphisms of the TLR-9 gene are correlated with atherogenesis. METHODS: The T-1237C and the T-1486C polymorphisms were analyzed by Real Time PCR in 202 (derivation study, age 58.1, SD 10.0) and 182 (validation study, age 59.7, SD 9.6) patients that underwent angioplasty and 188 healthy controls (age 52.5, SD 6.1). Restenosis was defined as >50% luminal diameter reduction at follow-up angiography. RESULTS: We found the two polymorphism being able to create new potential binding sites for transcription factors, however, no association of the TLR-9 polymorphisms with atherogenesis or restenosis was detectable. CONCLUSION: Our data indicate that the two TLR-9 promotor polymorphisms are not involved in atherogenesis.

A frequent toll-like receptor (TLR)-2 polymorphism is a risk factor for coronary restenosis.

Restenosis is a major problem for patients undergoing percutaneous transluminal coronary angioplasty (PTCA). Inflammatory processes and genetic factors have been suggested to be involved in the pathogenesis of both atherosclerosis and restenosis. The recently discovered family of Toll-like receptors (TLRs) consists of molecules that initiate signaling after host-pathogen interactions. Recently it has been shown that the TLRs are involved in the development and progression of atherosclerosis by interfering with lipid metabolisms and by mediating inflammation. TLR-2 is a key innate immunity receptor for sensing both endogenous inflammatory mediators and ligands of several microbial pathogens postulated to be involved in atherosclerosis. A frequent single nucleotide polymorphism (SNP) for the TLR-2 gene, resulting in a non-functional receptor, has been described. By genotyping two independent groups of patients receiving PTCA, followed by stent implantation in one group, we found a significantly enhanced frequency of the TLR-2 Arg753Gln SNP in patients with restenosis as compared to those without restenosis (PTCA: 7.21 versus 2.45%, P = 0.014; PTCA/stent: 6.86 versus 1.53%, P = 0.013). In contrast, a common TLR-4 SNP was similarly distributed among the patient groups investigated. We furthermore compared the frequency of both SNPs in the patients with an age-matched group of individuals without atherosclerosis and found a trend towards a lower frequency of the TLR-4 SNP in the atherosclerotic group (PTCA: 5.58; PTCA/stent: 3.85 versus 7.14%). We conclude that in restenosis a functional TLR-2 is protective and potentially involved in a reaction pattern preventing restenosis. Screening for the TLR-2 Arg753Gln SNP may be of importance for stratifying a patient's risk and for preventive and therapeutic measures.

Phenotypic variability in Hey2 -/- mice and absence of HEY2 mutations in patients with congenital heart defects or Alagille syndrome.

The genetic alterations leading to congenital heart defects (CHD) are still poorly understood. We and others have recently shown that in mice loss of Hey2 results in a high incidence of fatal ventricular and atrial septal defects, combined with tricuspid stenosis or atresia in some cases. The phenotype has been postulated to resemble human tetralogy of Fallot. Our analysis of CD1 outbred mice suggests that phenotypic consequences of Hey2 loss can be quite variable and dependent on modifier genes as we detected only isolated VSDs with lower prevalence and a significantly reduced mortality rate in this strain. Since Hey2 is one of the few Notch target genes, it is also conceivable that HEY2 mutations may account for cases of Alagille syndrome (AGS: variable combinations of heart, skeleton, eye, and facial malformations and cholestasis), in which the typical mutations of the Notch ligand JAG1 cannot be found. To clarify the role of HEY2 in human CHD and AGS, we screened by direct sequencing 23 children with CHD and 38 patients diagnosed with AGS, which lack mutations in the JAG1 gene. We found two types of silent changes in the coding region: a CTT-->CTG transition in exon 3 and a CTG-->CTC polymorphism in exon 5. Furthermore, a heterozygous SNP in the splice donor site of exon 4 was detected that is unlikely to disrupt splicing. Although the high incidence and variability of human congenital heart defects implies a multifactorial genetic basis, our results suggest that mutation of HEY2 is not a major contributing factor.