Lack of association of eNOS (G894T) and p22phox NADPH oxidase subunit (C242T) polymorphisms with systemic sclerosis in a cohort of French Caucasian patients

Endothelial nitric oxide synthase and nicotinamide adenosine dinucleotide phosphate oxidase p22phox gene (C242T) polymorphisms and systemic lupus erythematosus in a Chinese Population

Genetic polymorphisms in the endothelial nitric oxide synthase (eNOS) and nicotinamide adenosine dinucleotide phosphate (NADPH) oxidase p22phox are linked with the expression and/or progression of vascular disease. We hypothesized that these polymorphisms may influence the development and/or progression of systemic lupus erythematosus (SLE), given their linkage with vascular disease. DNA from patients with SLE (n = 90) and their age- and sex-matched controls (n = 86) from The Second Xiangya Hospital of Central South University was assessed for eNOS and NADPH oxidase p22phox polymorphisms. These polymorphisms were examined by restriction fragment length polymorphism-polymerase chain reaction. The allele frequency of the NADPH oxidase p22phox gene C242T polymorphisms significantly varied between the SLE patients and the controls. We found no association of the eNOS polymorphism with the development of renal disease. These results indicated that the etiology of patients with SLE is associated with NADPH oxidase p22phox gene C242T polymorphisms. There was no significant increased risk of SLE associated with eNOS polymorphisms in the Chinese population.

Genetic susceptibility to systemic sclerosis from clinical aspect to genetic factor analyses

BACKGROUND

Systemic sclerosis is a rare autoimmune disease mainly characterized by vascular alteration and fibrosis involving skin but also visceral organs such as lungs, digestive tract, and heart. This disease leads to high morbidity and mortality. Its pathogenesis remains unclear, but recent attention has focus on genetic factors.

OBJECTIVE

We first recall the main manifestations associated with systemic sclerosis and leading to its diagnosis and prognosis. Then we propose an overview on human genetics studies, as a number of genetic loci have been identified that appear to be associated with the disease.

METHODS

Articles concerning association studies with candidate genes encoding for extracellular matrix proteins, cytokines, growth factors, chemokines, and proteins involved in vascular tone and immune regulations are presented and discussed.

RESULTS/CONCLUSION

Systemic sclerosis is a multigenic complex disorder. Genetic associations are observed in distinct phenotypes such as the diffuse cutaneous form or the limited form, or in association with specific autoantibody pattern. Promising candidate genes are those involved in pathways that lead to the vascular damage and fibrosis. A better knowledge of crucial mediators involved in systemic sclerosis could in the future provide new therapeutic strategies to control the disease.

A polymorphism in the human serotonin 5-HT2A receptor gene may protect against systemic sclerosis by reducing platelet aggregation

INTRODUCTION

Platelet aggregation may contribute to the pathogenesis of systemic sclerosis: following activation, platelets release significant amounts of serotonin - which promotes vasoconstriction and fibrosis, and further enhances aggregation. The C+1354T polymorphism in the exonic region of the serotonin 2A receptor gene determining the His452Tyr substitution was associated with blunted intracellular responses after serotonin stimulation, and may have a role in susceptibility to scleroderma.

METHODS

One hundred and fifteen consecutive systemic sclerosis patients and 140 well-matched healthy control individuals were genotyped by sequence-specific primer-PCR for the His452Tyr substitution of the serotonin 2A receptor gene, and associations were sought with scleroderma and its main clinical features. The functional relevance of the His452Tyr substitution was also assessed by evaluating the aggregation of platelet-rich plasma from His452/His452 and His452/Tyr452 healthy individuals after stimulation with adenosine diphosphate +/- serotonin.

RESULTS

The T allele of the C+1354T polymorphism was underrepresented in scleroderma patients compared with control individuals (5.2% versus 12.4%, P < 0.001, chi-square test and 1,000-fold permutation test) and its carriage reduced the risk for systemic sclerosis (odds ratio = 0.39, 95% confidence interval = 0.19 to 0.85, P < 0.01). Platelets from His452/Tyr452 healthy subjects more weakly responded to serotonin stimulation compared with platelets from His452/His452 individuals (3.2 +/- 2.6-fold versus 9.6 +/- 8.6-fold increase in aggregation, P = 0.017 by Kolmogorov-Smirnov test and P = 0.003 after correction for baseline adenosine diphosphate-induced aggregation values).

CONCLUSION

The His452Tyr substitution may influence susceptibility to systemic sclerosis by altering platelet aggregation in response to serotonin.

Genetic basis for systemic sclerosis

Among the connective tissue diseases, systemic sclerosis is an orphan disease in which diffuse connective tissue alterations lead to multi-organ involvement. Environmental factors implicated in triggering this multifactorial disease include crystalline silica, chlorine solvents, welding vapors, and various other solvents. Clustering within families indicates a role for genetic factors. Although concordance for the disease among identical twins is low, concordance for autoantibodies associated with systemic sclerosis and for fibroblast gene expression profiles is higher. Because multiplex families are rare, association and candidate gene strategies are the most appropriate methods for investigating the genetics of systemic sclerosis. The most consistent data relate to the involvement of fibrosis genes, most notably the TGF-beta regulation pathway, secreted protein acid and rich in cysteine (SPARC) genes, and the fibrillin-1 gene (FBN1). Several variants of genes for cytokines or their receptors may be involved. Data on the vasculopathy characteristic of systemic sclerosis are somewhat conflicting. Investigations into the genetics of systemic sclerosis may shed light on the complex pathophysiology of this disease, help to identify factors that predict organ involvement, and suggest new treatment strategies.

Genetic factors in systemic sclerosis

A number of genetic loci have been identified that appear to be associated with systemic sclerosis (SSc; scleroderma). There is mounting evidence suggesting that these genetic associations may in fact be associated with distinct phenotypes in SSc based on autoantibody pattern rather than with SSc as a single disease entity. This may ultimately have implications for approaches to therapy as well as responses to therapy. The most promising candidate genes are those involved in pathways that lead to the vascular damage and fibrosis that are the hallmarks of this disease. There is uncertainty, however, regarding the nature of the key pathological mechanisms that link these two disease processes. Recent studies have focused on Fli1 (friend leukaemia integration 1), a transcription factor that is found in immune cells, fibroblasts, and endothelial cells that regulates collagen gene function and angiogenesis. Fli1 is dysregulated in SSc skin and dermal blood vessels, and appears to play a pathological role in SSc skin fibrosis and vessel degeneration. Whether this dysregulation is due to genetic polymorphisms in the Fli1 pathway or to epigenetic mechanisms is not clear.

Implication de l'interleukine 13 et de son récepteur dans la sclérodermie systémique

PURPOSE

Interleukin 13 is an immunoregulatory cytokine predominantly secreted by activated Th2 cells. It has similar functions with interleukin 4 and they share a common receptor. However, unlike interleukin 4, l'interleukin 13 does not appear to be important in the initial differentiation of CD4 T into Th2-type cells, but rather appears to be necessary in the effector phase of inflammation and fibrosis. This cytokine has been involved in recent works in allergic inflammation and in some fibrotic diseases leading to a scientific interest to analysis the role of interleukin 13 in systemic sclerosis (scleroderma).

MAIN POINTS

Systemic sclerosis is an autoimmune disease characterized by vascular alteration and skin and visceral fibrosis. A genetic background associated with susceptibility is supposed. Knowing the profibrogenic properties of interleukin 13, we asked if polymorphisms located in interleukin 13 and interleukin 13 receptor genes could be associated with systemic sclerosis. We observed significant associations between IL13 and IL13RA2 gene polymorphisms and the disease, particularly the cutaneous diffuse form of the disease.

PERSPECTIVES AND PROJECTS

Results concerning the involvement of interleukin 13 pathway in systemic sclerosis need to be confirmed on another larger population. Functional studies will be done to explain the effect of these associations. We feel that IL13/IL13R pathway is interesting as immunomodulation with the interleukin 13 receptor inhibitor is possible in therapy.

Evidence of potential interaction of chemokine genes in susceptibility to systemic sclerosis

OBJECTIVE

To examine genetic polymorphisms in the chemokine pathway, and to assess their interactions in relation to susceptibility to systemic sclerosis (SSc).

METHODS

To identify the risk of SSc conferred by genetic polymorphisms in the chemokine pathway, 10 single-nucleotide polymorphisms (SNPs) from 8 candidate genes were studied in 99 patients with SSc and 198 age- and sex-matched controls in a Korean population. SNPs were genotyped by polymerase chain reaction-restriction fragment length polymorphism or sequence-specific primer methods. Genetic associations between each SNP and SSc risk, calculated as odds ratios with 95% confidence intervals, were estimated using chi-square tests. Haplotypes for the 2 polymorphisms in the gene CCL5 (RANTES) were constructed, and their associations with SSc were tested. Gene-gene interactions were investigated using a recently described novel method, and the results were confirmed by conditional logistic regression. Adjustment for multiple testing was based on Bonferroni correction.

RESULTS

There was significant evidence of gene-gene interaction between polymorphisms in the genes CXCL8 (interleukin-8) and CCL5, and both of these were associated with an increased risk of SSc. This SNP-SNP interaction was confirmed by 2 independent statistical methods. The associations remained significant after Bonferroni adjustment for multiple testing. No significant association between each individual SNP or haplotype and the risk of SSc was found.

CONCLUSION

Crosstalk between the 2 chemokines CXCL8 and CCL5 may contribute to the susceptibility to SSc.

Hemorheologic profile in systemic sclerosis: role of NOS3 -786T > C and 894G >T polymorphisms in modulating both the hemorheologic parameters and the susceptibility to the disease

OBJECTIVE

Microvascular disorders are relevant in systemic sclerosis (SSc). Hyperviscosity, due to alterations of blood cells and plasma components, may play a role in the pathogenesis of microcirculatory disorders. An impaired availability of nitric oxide, related to polymorphisms in NOS3, the gene for endothelial cell nitric oxide synthase, might influence erythrocyte deformability. We undertook this study to investigate the hemorheologic profile in SSc and the role of NOS3 polymorphisms in modulating the hemorheologic status of SSc patients.

METHODS

We studied 113 consecutive SSc patients (75 with limited cutaneous SSc [lcSSc] and 38 with diffuse cutaneous SSc [dcSSc]) and 113 healthy controls. The hemorheologic profile was obtained by assessing whole blood viscosity (WBV; at shear rates of 0.512 and 94.5 seconds(-1)), plasma viscosity (PLV; at a shear rate of 94.5 seconds(-1)), and erythrocyte deformability index (DI). We determined NOS3 polymorphisms by molecular analysis.

RESULTS

A marked alteration of hemorheologic parameters was found both in patients with lcSSc and in those with dcSSc compared with controls (P < 0.0001). In multivariate analysis, rheologic variables were significantly associated with the disease (for WBV at a shear rate of 94.5 seconds(-1), odds ratio [OR] 5.4, 95% confidence interval [95% CI] 1.4-19.9, P = 0.01; for PLV, OR 2.8, 95% CI 1.2-6.5, P = 0.01; for DI, OR 3.9, 95% CI 1.4-10.8, P = 0.007), and NOS3 -786C and 894T alleles significantly affected the DI (for -786C allele, OR 2.3, 95% CI 1.01-5.4, P = 0.04; for 894T allele, OR 2.2, 95% CI 1.01-4.8, P = 0.04). The simultaneous presence of the -786C and 894T alleles represented a susceptibility factor for SSc (OR 2.8, 95% CI 1.4-5.7, P = 0.004).

CONCLUSION

Our findings document an altered rheologic profile in SSc and demonstrate a relationship between this alteration and NOS3 polymorphisms, thus shedding light on a potential novel mechanism influencing the microcirculation in this disease.

Inducible and endothelial nitric oxide synthase genes polymorphism in inflammatory bowel disease

To assess the influence of inducible and endothelial nitric oxide synthase gene (NOS2A and NOS3) polymorphisms in susceptibility to Crohn's disease (CD) and ulcerative colitis (UC). A total of 505 inflammatory bowel disease (IBD) patients (221 with UC and 284 with CD) and 332 ethnically matched controls were studied. Patients and controls were genotyped by polymerase chain reaction -based techniques for a multiallelic (CCTTT)(n) repeat and biallelic marker (TAAA)(n) in the promoter region of the NOS2A gene and for a T/C polymorphism at position -786 in the promoter region and a polymorphism in exon 7(298Glu/Asp) of the NOS3 gene. There was not association between NOS2A and NOS3 genotypes, alleles or haplotypes frequencies with UC, CD and controls. Our data suggest that NOS2A and NOS3 polymorphisms do not play a major role in IBD predisposition.

NAD(P)H oxidase p22phox gene C242T polymorphism, nitric oxide production, salt sensitivity and cardiovascular risk factors in Hispanics

Mutations in the NAD(P)H oxidase gene may be associated with abnormal superoxide generation, nitric oxide (NO) availability and cardiovascular diseases. We investigated the prevalence of the NAD(P)H oxidase p22phox gene C242T polymorphism, and its possible association with blood pressure, NO production, salt sensitivity and cardiovascular risk factors in Hispanics. Genotype frequencies were as follows: CC, 52.9%; CT, 40.3%; and TT, 6.8%. There were no significant differences in systolic blood pressure, diastolic blood pressure, age, weight, fasting and post-load glucose levels, LDL and HDL cholesterol, triglyceride and urinary albumin levels in subjects with CC, CT or the TT genotypes. Presence of the T allele was associated with increased salt sensitivity in women, but not in men. NO metabolite excretion was markedly decreased both in women and men with the TT genotype (CC: 868+/-79 micromol/day; CT: 839+/-75 micromol/day; TT: 534+/-78 micromol/day; P<0.05). In conclusion, the prevalence of the NAD(P)H oxidase p22phox gene C242T polymorphism in Venezuelans was comparable to that of Caucasians, but different from that of Chinese and Japanese. Although the T allele was not associated with cardiovascular risk factors, hyperinsulinaemia or hypertension, in women, it appeared to be a genetic susceptibility factor for salt sensitivity. Both in women and men, the p22phox gene may play a role in the genetic control of NO levels.

Genetics of scleroderma: update on single nucleotide polymorphism analysis and microarrays

PURPOSE OF REVIEW

Recent family, twin, and genetic association studies suggest a genetic basis for the susceptibility to systemic sclerosis or scleroderma. The purpose of this review is to summarize the results of genetic association and gene expression profiling studies from January 2004 to May 2005.

RECENT FINDINGS

In the review period, only a handful reports on single nucleotide polymorphism analysis of candidate genes and transcriptional profiling have been published.

SUMMARY

Currently, single nucleotide polymorphism association studies in systemic sclerosis use small sample sizes and have low reproducibility. To detect associations with candidate genes that confer a modest relative risk for disease in the general population, studies are needed with much larger sample sizes that also account for the effects of population stratification. Candidate genes or pathways identified through microarrays can be explored as potential biomarkers, used for molecular phenotyping of systemic sclerosis, or targeted for future genetic association studies.