NOS2 polymorphisms associated with the susceptibility to pulmonary arterial hypertension with systemic sclerosis: contribution to the transcriptional activity

Updates on genetics in systemic sclerosis

Systemic sclerosis (SSc) is a complex disease, in which an interaction of genetic and environmental factors plays an important role in its development and pathogenesis. A number of genetic studies, including candidate gene analysis and genome-wide association study, have found that the associated genetic variants are mainly localized in noncoding regions in the expression quantitative trait locus and influence corresponding gene expression. The gene variants identified as a risk for SSc susceptibility include those associated with innate immunity, adaptive immune response, and cell death, while there are only few SSc-associated genes involved in the fibrotic process or vascular homeostasis. Human leukocyte antigen class II genes are associated with SSc-related autoantibodies rather than SSc itself. Since the pathways between the associated genotype and phenotype are still poorly understood, further investigations using multi-omics technologies are necessary to characterize the complex molecular architecture of SSc, identify biomarkers useful to predict future outcomes and treatment responses, and discover effective drug targets.

The Role of Inducible NOS2 Gene Polymorphism in the Development of Essential Arterial Hypertension

The risk of essential arterial hypertension was assessed in carriers of the NOS2 gene variants (rs1800482 (-954G>C), rs3730017 (C>T)). In subjects carrying C allele (rs1800482), the risk for essential arterial hypertension developing was higher by 1.7 times (OR=1.712, 95%CI 1.07-2.74), while the presence of T-allele (rs3730017) had a protective effect (OR=0.304, 95%CI 0.192-0.482). In patients with essential arterial hypertension, the presence of the C allele (rs1800482) was associated with a higher content of NO metabolites in the blood plasma. A positive correlation was found between the plasma content of nitrites and nitrates and the level of transcripts of VCAM1, ICAM1 genes in peripheral blood leukocytes. We found the influence of the C allele carriership on the expression VCAM1 and ICAM1 genes in patients with essential hypertension. It was hypothesized that this polymorphic site in the NOS2 gene can be involved in the development of endothelial dysfunction and essential arterial hypertension through modulation of NO level under condition of inflammation.

Polymorphisms in oxidative pathway related genes and susceptibility to inflammatory bowel disease

AIM

To investigate whether common variants in the oxidative pathway genes influence inflammatory bowel disease (IBD) risk among Moroccan patients.

METHODS

The distribution of (TAAA)n_rs12720460 and (CCTTT)n _rs3833912 NOS2A microsatellite repeats, HIF-1A_rs11549467 and NFKB1-94ins/delATTG_rs28362491 was analyzed in 507 subjects grouped in 199 IBD and 308 healthy controls. Genotyping was performed with polymerase chain reaction-fluorescent method and the TaqMan^® allelic discrimination technology.

RESULTS

The allele and genotype frequencies of HIF1A_ rs11549467, NFKB1_rs28362491 and NOS2A_ (TAAA)n did not differ significantly between patients and controls. Analysis of NOS2A_ (CCTTT)n markers evidenced differences between patients and healthy controls. A preferential presence of the (CCTTT)8 (P = 0.02; OR = 1.71, 95%CI: 1.07-2.74), (CCTTT)14 (P = 0.02; OR = 1.71, 95%CI: 1.06-2.76) alleles in IBD, (CCTTT)8 (P = 0.008; OR = 1.95, 95%CI: 1.17-3.23) in CD and (CCTTT)7 (P = 0.009; OR = 7.61, 95%CI: 1.25-46.08), (CCTTT)11 (P = 0.05; OR = 0.51, 95%CI: 0.25-1.01), (CCTTT)14 (P = 0.02; OR = 2.05, 95%CI: 1.07-3.94), (CCTTT)15 (P = 0.01; OR = 2.25, 95%CI: 1.16-4.35) repeats in UC patients indicated its possible association with higher disease risk which need to be confirmed in a larger sample size.

CONCLUSION

Our results suggest that the NOS2A_ (CCTTT)n gene variations may influence IBD susceptibility in the Moroccan population.

A systematic review of genetic mutations in pulmonary arterial hypertension

Background

Pulmonary arterial hypertension (PAH) is a group of vascular diseases that produce right ventricular dysfunction, heart failure syndrome, and death. Although the majority of patients appear idiopathic, accumulated research work combined with current sequencing technology show that many gene variants could be an important component of the disease. However, current guidelines, clinical practices, and available gene panels focus the diagnosis of PAH on a relatively low number of genes and variants associated with the bone morphogenic proteins and transforming Growth Factor-β pathways, such as the BMPR2, ACVRL1, CAV1, ENG, and SMAD9.

Methods

To provide an expanded view of the genes and variants associated with PAH, we performed a systematic literature review. Facilitated by a web tool, we classified, curated, and annotated most of the genes and PubMed abstracts related to PAH, in which many of the mutations and variants were not annotated in public databases such as ClinVar from NCBI. The gene list generated was compared with other available tests.

Results

Our results reveal that there is genetic evidence for at least 30 genes, of which 21 genes shown specific mutations. Most of the genes are not covered by current available genetic panels. Many of these variants were not annotated in the ClinVar database and a mapping of these mutations suggest that next generation sequencing is needed to cover all mutations found in PAH or related diseases. A pathway analysis of these genes indicated that, in addition to the BMP and TGFβ pathways, there was connections with the nitric oxide, prostaglandin, and calcium homeostasis signalling, which may be important components in PAH.

Conclusion

Our systematic review proposes an expanded gene panel for more accurate characterization of the genetic incidence and risk in PAH. Their usage would increase the knowledge of PAH in terms of genetic counseling, early diagnosis, and potential prognosis of the disease.

Electronic supplementary material

The online version of this article (doi:10.1186/s12881-017-0440-5) contains supplementary material, which is available to authorized users.

Inducible nitric oxide synthase gene polymorphisms are associated with a risk of nephritis in Henoch-Schönlein purpura children

Henoch-Schönlein purpura (HSP) is the most common form of systemic small-vessel vasculitis in children, and HSP nephritis (HSPN) is a major complication of HSP and is the primary cause of morbidity and mortality. Previous studies have suggested that inducible nitric oxide synthase (iNOS) may play an important role in the pathogenesis of HSP. In this study, we performed a detailed analysis to investigate the potential association between iNOS polymorphisms and the risk of HSP and the tendency for children with HSP to develop HSPN in a Chinese Han population. A promoter pentanucleotide repeat (CCTTT)n and 10 functional single-nucleotide polymorphisms (SNPs) from 532 healthy controls and 513 children with HSP were genotyped using the MassARRAY system and GeneScan. The results suggested that the allelic and genotypic frequencies of the rs3729508 polymorphism were nominally associated with susceptibility to HSP. In addition, there was a significant difference in the allelic distribution of the (CCTTT)12 repeats and rs2297518 between the HSP children with and without nephritis; the HSP children with nephritis exhibited a significantly higher frequency of the (CCTTT)12 repeats and A allele of rs2297518 than the HSP children without nephritis (P _FDR = 0.033, OR = 1.624, 95% CI = 1.177-2.241 and P _FDR = 0.030, OR = 1.660, 95% CI = 1.187-2.321, respectively).

CONCLUSION

Our results support that iNOS polymorphisms are associated with the risk of HSP and may strongly contribute to the genetic basis of individual differences in the progression to nephritis among children with HSP in the Chinese Han population. What is Known: • The etiology of HSP is unknown, but the genetic factors may play an important role in the pathogenesis of HSP. • iNOS could contribute to the development and clinical manifestations of HSP, and this has not been studied extensively so far. What is New: • Our results support that iNOS polymorphisms not only are associated with HSP risk but also strongly contribute to the genetic basis of individual differences in the progression of HSP to nephritis among Chinese Han children.

Exhaled Nitric Oxide in Systemic Sclerosis Lung Disease

Background. Exhaled nitric oxide (eNO) is a potential biomarker to distinguish systemic sclerosis (SSc) associated pulmonary arterial hypertension (PAH) and interstitial lung disease (ILD). We evaluated the discriminative validity, feasibility, methods of eNO measurement, and magnitude of differences across lung diseases, disease-subsets (SSc, systemic lupus erythematosus), and healthy-controls. Methods. Consecutive subjects in the UHN Pulmonary Hypertension Programme were recruited. Exhaled nitric oxide was measured at 50 mL/s intervals using chemiluminescent detection. Alveolar and conducting airway NO were partitioned using a two-compartment model of axial diffusion (CMAD) and the trumpet model of axial diffusion (TMAD). Results. Sixty subjects were evaluated. Using the CMAD model, control subjects had lower median (IQR) alveolar NO than all PAH subjects (2.0 (1.5, 2.5) versus 3.14 ppb (2.3, 4.0), p = 0.008). SSc-ILD had significantly lower median conducting airway NO compared to controls (1009.5 versus 1342.1 ml⁎ppb/s, p = 0.04). SSc-PAH had increased median (IQR) alveolar NO compared to controls (3.3 (3.0, 5.7) versus 2.0 ppb (1.5, 2.5), p = 0.01). SSc-PAH conducting airway NO inversely correlated with DLCO (r -0.88 (95% CI -0.99, -0.26)). Conclusion. We have demonstrated feasibility, identified that CMAD modeling is preferred in SSc, and reported the magnitude of differences across cases and controls. Our data supports discriminative validity of eNO in SSc lung disease.

Association evidence of CCTTT repeat polymorphism in the iNOS promoter and the risk of atrial fibrillation in Taiwanese

Inducible nitric oxide synthase (iNOS) plays an important role in the pathogenesis of atrial fibrillation (AF). The iNOS promoter has a CCTTT-repeat length polymorphism that can determine the level of gene transcription. This study enrolled 200 AF patients and 240 controls. The length of CCTTT-repeat polymorphism in the iNOS promoter region was examined by polymerase chain reactions, with the alleles with ≤11 repeats designated as S and alleles with ≥12 repeats designated as L alleles. AF patients carried significantly higher frequencies of the LL genotype than control subjects (40.0% versus 28.3%, P = 0.010). Multivariate analysis showed that the presence of LL genotype was significantly associated with AF (odds ratio: 1.87, 95% CI = 1.10–3.17, P = 0.021). In vitro, transient transfection assay in HL-1 atrial myocytes showed that the responsiveness of iNOS transcriptional activity to tachypacing was correlated with the length of the CCTTT-repeats. Right atrial tissues from patients with chronic AF were investigated with immunoconfocal microscopy. Patients with LL genotype exhibited greater oxidative stress and substrate remodeling in their atria than those with non-LL genotypes. Our results suggest that the iNOS microsatellite polymorphism may contribute to the genetic background of AF in Chinese-Taiwanese patients.

Outcome after BCG treatment for urinary bladder cancer may be influenced by polymorphisms in the NOS2 and NOS3 genes

Purpose

Bacillus Calmette-Guérin (BCG)-treatment is an established treatment for bladder cancer, but its mechanisms of action are not fully understood. High-risk non-muscle invasive bladder-cancer (NMIBC)-patients failing to respond to BCG-treatment have worse prognosis than those undergoing immediate radical cystectomy and identification of patients at risk for BCG-failure is of high priority. Several studies indicate a role for nitric oxide (NO) in the cytotoxic effect that BCG exerts on bladder cancer cells. In this study we investigated whether NO-synthase (NOS)-gene polymorphisms, NOS2-promoter microsatellite (CCTTT)n, and the NOS3-polymorphisms-786T>C (rs2070744) and Glu298Asp (rs1799983), can serve as possible molecular markers for outcome after BCG-treatment for NMIBC.

Materials and methods

All NMIBC-patients from a well-characterized population based cohort were analyzed (n=88). Polymorphism data were combined with information from 15-years of clinical follow-up. The effect of BCG-treatment on cancer-specific death (CSD), recurrence and progression in patients with varying NOS-genotypes were studied using Cox proportional hazard-models and log rank tests.

Results

BCG-treatment resulted in significantly better survival in patients without (Log rank: p=0.006; HR: 0.12, p=0.048), but not in patients with a long version ((CCTTT)n ≧13 repeats) of the NOS2-promoter microsatellite. The NOS3-rs2070744(TT) and rs1799983(GG)-genotypes showed decreased risk for CSD (Log rank(TT): p=0.001; Log rank(GG): p=0.010, HR(GG): 0.16, p=0.030) and progression (Log rank(TT): p<0.001, HR(TT): 0.05, p=0.005; Log rank(GG): p<0.001, HR(GG): 0.10, p=0.003) after BCG-therapy compared to the other genotypes. There was also a reduction in recurrence in BCG-treated patients that was mostly genotype independent. Analysis of combined genotypes identified a subgroup of 30% of the BCG-treated patients that did not benefit from BCG-treatment.

Conclusions

Our results suggest that the investigated polymorphisms influence patient response to BCG-treatment and thus may serve as possible markers for identification of BCG-failures.

•

30% of BCG treated bladder cancer (NMIBC)-patients do not respond to BCG-treatment.

•

We need to identify BCG failures before the BCG-treatment is given.

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Altered NOS2 and NOS3 gene activity may be associated with BCG treatment outcome.

•

NOS-polymorphisms are possible BCG-failure biomarkers in bladder cancer patients.

Polymorphisms in oxidative stress-related genes are associated with nasopharyngeal carcinoma susceptibility

Nasopharyngeal carcinoma (NPC) is a complex multifactorial disorder involving both genetic and environmental factors. Polymorphisms of genes encoding nitric oxide synthase (NOS) and antioxidant glutathione-S transferases (GSTs) have been associated with various tumors. We examined the combined role of NOS3, NOS2 and GST polymorphisms in NPC risk in Tunisians. We found that NOS3−786C allele and −786 CC genotype, NOS3+894T allele and +894 GT+TT genotypes, NOS2−277 G allele and −277 GG genotype, and GSTT1 del/del genotype, are more prevalent in NPC patients as compared to healthy controls. Our results suggest that genetically driven dysfunction in red–ox stress pathway could augment the risk in NPC-susceptible individuals.

Pathogenesis of Systemic Sclerosis

Systemic scleroderma (SSc) is one of the most complex systemic autoimmune diseases. It targets the vasculature, connective tissue-producing cells (namely fibroblasts/myofibroblasts), and components of the innate and adaptive immune systems. Clinical and pathologic manifestations of SSc are the result of: (1) innate/adaptive immune system abnormalities leading to production of autoantibodies and cell-mediated autoimmunity, (2) microvascular endothelial cell/small vessel fibroproliferative vasculopathy, and (3) fibroblast dysfunction generating excessive accumulation of collagen and other matrix components in skin and internal organs. All three of these processes interact and affect each other. The disease is heterogeneous in its clinical presentation that likely reflects different genetic or triggering factor (i.e., infection or environmental toxin) influences on the immune system, vasculature, and connective tissue cells. The roles played by other ubiquitous molecular entities (such as lysophospholipids, endocannabinoids, and their diverse receptors and vitamin D) in influencing the immune system, vasculature, and connective tissue cells are just beginning to be realized and studied and may provide insights into new therapeutic approaches to treat SSc.

The (CCTTT) n pentanucleotide repeat polymorphism in the inducible nitric oxide synthase gene promoter and the risk of psoriasis in Taiwanese

Recently, genome-wide association studies identified a novel psoriasis susceptibility locus tagged by two single-nucleotide polymorphisms (SNPs) rs4795067 and rs28998802, both of which are in the intronic region of inducible nitric oxide synthase (iNOS) gene. This study aimed to assess the role of (CCTTT) n pentanucleotide repeat polymorphisms in the promoter region of iNOS gene in Chinese-Taiwanese patients with psoriasis. In total, 280 patients with psoriasis and 512 control subjects were analyzed for the presence of the iNOS microsatellite polymorphism by polymerase chain reactions. The alleles were classified as S and L alleles according to the number of (CCTTT) n repeats, with the alleles with ≤13 repeats designated as S and alleles with ≥14 repeats designated as L alleles. The distribution of allele frequencies and genotypes was significantly different between the control and psoriasis groups (P = 0.040, and 0.014, respectively). After adjustment for age, sex, body mass index, smoking, diabetes, and hypertension, carriers of the LL genotype were 0.38 (95% confidence interval 0.16-0.95) times less likely than non-carriers to have psoriasis (P = 0.038). The promoter assays demonstrated that the iNOS promoter activity increases in parallel with the repeat number of (CCTTT) n in HaCaT cells. Approximately 70% of the study subjects were genotyped for rs4795067 and rs28998802. The rs4795067 is in linkage disequilibrium with the microsatellite L/S allelic classification. The association of iNOS microsatellite with psoriasis is independent of these known iNOS variants. Our results suggest that the iNOS microsatellite may contribute to the genetic background of psoriasis in Chinese-Taiwanese patients.

CCTTT pentanucleotide repeats in inducible nitric oxide synthase gene expression in patients with pulmonary arterial hypertension

INTRODUCTION

One of the pathways involved in pulmonary arterial hypertension (PAH) is the nitric oxide (NO) pathway. A polymorphism in the inducible NO synthase (NOS2) gene has been described, consisting of the CCTTT pentanucleotide repeat, which causes a reduction in NO production. The aim of this study was to determine if this polymorphism increases susceptibility to developing PAH.

METHODS

Sixty four patients with a diagnosis of PAH groupsi and iv and 50 healthy controls were compared. DNA genotyping of the samples for this polymorphism was performed using PCR. The distribution between both groups was compared and correlated with clinical and haemodynamic parameters and therapeutic response.

RESULTS

A significantly different distribution was observed in the number of repeats between patients and controls (P<.0001). When the samples were categorised by short forms (both alleles with less than 12repeats) and long forms (≥12 repeats), it was observed that the former had an almost 4-fold risk of developing PAH (odds ratio: 3.83; 95%CI: 1.19-12.32, P=.024). There were no differences between the most common types of PAH, either in therapeutic response or survival. There was no correlation between haemodynamic parameters and the number of repeats in the patients, and only a weak correlation with systolic PAH.

CONCLUSIONS

There are significant differences in the distribution of the NOS2 promotor CCTTT polymorphism between patients with PAH and the healthy population. A minor CCTTT pentanucleotide repeat in the NOS2 gene may increase the risk of developing PAH.

The (CCTTT)n microsatellite polymorphism in the NOS2 gene may influence lung cancer risk and long-term survival, especially in non-smokers

We analyzed the associations of the NOS2 (CCTTT)n promoter polymorphism to lung cancer risk and tumor histology in smokers and non-smokers. We also investigated lung cancer long-term survival in relation to the polymorphism, smoking data, histology, age at diagnosis, and gender. One hundred eighty-five lung-cancer patients and 164 matched controls, where non-smokers were enriched among the lung cancer cases, were genotyped by fragment analysis and sequencing. Genotypes were combined with information on histology, patient smoking status, and cancer-specific death, using a 20-year follow-up. We divided the (CCTTT)n alleles into short (n ≤ 10), intermediate (n = 11-12), and long (n ≥ 13). Patients homozygous for short repeats had significantly increased risk of lung cancer (p = 0.030) compared to carriers of two long alleles (LL). Lack of long allele was associated with a significantly increased lung cancer risk overall (p = 0.011), especially among non-smokers (p = 0.001). A significantly higher lung cancer survival was seen in non-smokers compared to smokers (p = 0.046) and in low-dose smokers compared to high-dose smokers at the time of diagnosis (p = 0.028). Moreover, non-smoking patients with squamous cell carcinoma (p = 0.015) or adenocarcinoma (p = 0.024) showed a significantly lower survival compared to other lung carcinomas. Nitric oxide can induce proliferation as well as apoptosis depending on cellular context. Our results suggest that the (CCTTT)n NOS2 microsatellite may influence the risk of developing lung cancer, especially in non-smokers, possibly by affecting intracellular nitric oxide levels. Our results also give additional information about the yet poorly understood etiological and prognostic differences between lung cancer in non-smokers and smokers.

Genetic markers of cardiovascular disease in rheumatoid arthritis

Cardiovascular (CV) disease is the most common cause of premature mortality in patients with rheumatoid arthritis (RA). It is the result of an accelerated atherosclerotic process. Both RA and atherosclerosis are complex polygenic diseases. Besides traditional CV risk factors and chronic inflammation, a number of studies have confirmed the role of genetic factors in the development of the atherogenesis observed in RA. In this regard, besides a strong association between the HLA-DRB1∗04 shared epitope alleles and both endothelial dysfunction, an early step in the atherosclerotic process, and clinically evident CV disease, other polymorphisms belonging to genes implicated in inflammatory and metabolic pathways, located inside and outside the HLA region, such as the 308 variant (G > A, rs1800629) of the TNFA locus, the rs1801131 polymorphism (A > C; position + 1298) of the MTHFR locus, or a deletion of 32 base pairs on the CCR5 gene, seem to be associated with the risk of CV disease in patients with RA. Despite considerable effort to decipher the genetic basis of CV disease in RA, further studies are required to better establish the genetic influence in the increased risk of CV events observed in patients with RA.

Unraveling the genetic component of systemic sclerosis

Systemic sclerosis (SSc) is a severe connective tissue disorder characterized by extensive fibrosis, vascular damage, and autoimmune events. During the last years, the number of genetic markers convincingly associated with SSc has exponentially increased. In this report, we aim to offer an updated review of the classical and novel genetic associations with SSc, analyzing the firmest and replicated signals within HLA and non-HLA genes, identified by both candidate gene and genome-wide association (GWA) studies. We will also provide an insight into the future perspectives and approaches that might shed more light into the complex genetic background underlying SSc. In spite of the remarkable advance in the field of SSc genetics during the last decade, the use of the new genetic technologies such as next generation sequencing (NGS), as well as the deep phenotyping of the study cohorts, to fully characterize the genetic component of this disease is imperative.

Pulmonary Arterial Hypertension-A Deadly Complication of Systemic Sclerosis

Pulmonary arterial hypertension (PAH) is a devastating disease with limited therapeutic options. Moreover, when PAH occurs in patients diagnosed with systemic sclerosis, worse outcomes are observed. The purpose of this review is to discuss the etiologies of PAH found in the systemic sclerosis patient, limitations of current medical therapies, and, finally, potential therapies for patients with this combination.

Association of the pentanucleotide repeat polymorphism in NOS2 promoter region with susceptibility to migraine in a Chinese population

Genes involved in the production of nitric oxide (NO) have been suggested as genetic factors for migraine. It has been studied whether polymorphisms in the genes encoding for different types of NO synthase (NOS) could be involved in the liability to migraine; however, most studies yield negative results. The pentanucleotide repeat microsatellite in the promoter region of inducible NOS (NOS2) shows highly significant differences in allelic frequencies among ethnically diverse populations. Thus, variation in the number of pentanucleotide repeats may have some significance in the predisposition to migraine among different human populations. The aim of this study was to investigate the possible association between pentanucleotide repeat polymorphism and the risk for migraine in Chinese population. We studied the genotypic and allelic frequencies of the pentanucleotide repeat polymorphism in the promoter region of NOS2 in 504 patients with migraine and 512 healthy controls, using polymerase chain reaction amplification and polyacrylamide gel electrophoresis analyses. Comparison of global allele counts between patients and controls showed that the difference was significant (p = 0.0014). The carriage of 9-repeat and 10-repeat alleles was significantly more common in controls, whereas 11-repeat allele was more common in patients after Bonferroni correction for multiple comparisons. A specific analysis of the different cutoffs for number of repeats showed that allelic and genotypic frequencies for the 9-repeat and 10-repeat cutoff were significantly different between cases and controls (p = 0.007 and p = 0.005 for allelic frequencies, respectively; p = 0.0086 and p = 0.0033 for genotypic frequencies, respectively). Our results implied an association between NOS2 pentanucleotide repeat polymorphism and migraine susceptibility in a Chinese population. Considering the significant allelic frequency differences in ethnically diverse populations, further replication studies, especially in ethnically different groups, were necessary to fully establish the role of NOS2 polymorphism in migraine susceptibility.

Two polypyrimidine tracts in the nitric oxide synthase 2 gene: similar regulatory sequences with different properties

We reported previously that the polymorphic polypyrimidine CCTTT-microsatellite in the regulatory region of nitric oxide synthase 2 (NOS2) bound nuclear proteins in vitro. In the present work, we aimed to characterize and investigate a potential regulatory role of the CCTTT-microsatellite in NOS2 expression. Therefore, we performed gel-shift, S1-nuclease, and chromatin immunoprecipitation (ChIP) assays. In vitro experiments showed that the microsatellite formed triplex-DNA both with and without superhelical constraint. We also found that the CCTTT-microsatellite and an apparently similar CT-repeat in the first intron of NOS2 were specifically cleaved by S1-nuclease, when cloned into a supercoiled plasmid. In vitro data suggested that the CCTTT-microsatellite bound both polypyrimidine tract-binding protein (PTBP1) and heterogeneous nuclear ribonucleoprotein K (hnRNPK). On the contrary, ChIP revealed binding of PTBP1 and hnRNPK rather to the CT-repeat in the first intron than to the CCTTT-microsatellite. Enrichment for RNA polymerase II and acetylated histones H3 and H4 was also detected at the intronic site. We suggest that both PTBP1 and hnRNPK binds the single strand of the triplex-DNA formed at the CT-repeat in the first intron and that this interaction could be involved in the regulation of NOS2 expression.

Endothelin receptor selectivity: evidence from in vitro and pre-clinical models of scleroderma

Scleroderma [systemic sclerosis (SSc)] is a spectrum of connective tissue diseases characterized by micro- and macro-vasculopathy, inflammation and autoimmunity and tissue remodelling that often leads to excessive scarring and fibrosis in both interstitial and vascular compartments. Pre-clinical investigations and gene association studies have led to improved understanding of the cell and molecular mechanisms underlying disease pathogenesis and to the identification of key molecular candidates that may represent potentially useful disease biomarkers and effective therapeutic targets. Studies on the endothelin (ET) system, pre-dominantly ET-1 and the cell surface receptors [type A (ET(A))] and type B (ET(B))], have provided evidence for an important role of this system in the vascular and fibrotic pathologies in SSc. To date, promising clinical results, utilizing dual/mixed ET receptor antagonism have been obtained in two of the vascular complications associated with SSc, ischaemic digital ulceration and pulmonary arterial hypertension. Evidence suggests that ET-1 is able to activate and re-program the functional phenotypes of vascular smooth muscle cells, microvascular pericytes and tissue fibroblasts into pro-fibrogenic cell populations with myofibroblasts-like properties. The impact of receptor-selective, over mixed-receptor, antagonism has also been studied in vitro with respect to cell differentiation and proliferation, extracellular matrix synthesis, production and deposition and in pathological cellular contraction. However, the complexity of the ET system, potential for receptor cross-talk, interactions with down-stream signal transduction cascades, as well as the potent inter-relationships with other important ligand-receptor pathways have made in vivo studies difficult to unravel. Moreover, little information is available on the role of the ET system and receptor selectivity in the recruitment and activation of mesenchymal progenitor cells in tissue remodelling and fibrosis or on the early inflammatory response. Here, we discuss the available pre-clinical evidence for the role of the ET system in tissue repair, scarring and fibrosis, using the connective tissue diseases SSc and model systems of fibrogenesis.

Genetics and genomic studies in scleroderma (systemic sclerosis)

It currently is believed that scleroderma is a complex polygenic disease that occurs in genetically predisposed individuals who have encountered specific environment exposures and/or other stochastic factors. The nature of these genetic determinants and how they interact with environmental factors are areas of active investigation. This article discusses the evidence that supports a strong genetic link to scleroderma. These studies implicate potential pathogenetic mechanisms involved in scleroderma, which, it is hoped, may translate into clinical utility, including determination of disease risk, diagnosis, prognosis, and novel therapeutics.

Endothelin receptor antagonists for pulmonary arterial hypertension: rationale and place in therapy

The last decade has seen significant advances in the understanding and treatment of pulmonary arterial hypertension (PAH). Three main pathways, involving endothelin, nitric oxide, and prostacyclin, have been identified in its pathogenesis and these have all led to the development of therapies in current use. While the nitric oxide and prostacyclin pathways require augmentation, the endothelin system is overactive in PAH, with increased endothelin synthesis and receptor expression and, therefore, requires blockade. There are two known endothelin receptors. The type A receptor, expressed in pulmonary artery media, mediates vasoconstriction and remodeling, whereas the function of the type B receptor is more complex. Like the type A receptor, the type B receptor mediates vasoconstriction and remodeling effects when expressed on smooth muscle cells and (myo)fibroblasts, yet functions to clear endothelin from the circulation and induce release of endogenous nitric oxide and prostacyclin, when activated in the pulmonary artery endothelium. Consequently, it is not clear from in vitro data whether the optimal strategy is to block only the type A receptor or both receptors. Phase III clinical studies show clear short-term physiologic benefit with both dual and selective endothelin blockade in PAH. Longer-term experience with bosentan, a dual receptor antagonist, has shown improved outcomes compared with historic control data and comparable survival to intravenous prostacyclin therapy. The newer selective blockers, sitaxsentan and ambrisentan, appear to have similar short-term efficacy, but long-term data are as yet either lacking or unpublished. They may be less hepatotoxic than bosentan, although long-term follow-up of patients receiving bosentan has shown this is not a significant problem. On the basis of available evidence, the endothelin receptor antagonists have become first-line therapy for patients with PAH, except in the most severely affected who still require treatment with intravenous prostacyclin. Although their use as part of combination therapy with other agents is widespread, the evidence for this is not as robust, but appropriate investigation is underway.

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.

Pathogenic mechanisms of pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a complex disease that causes significant morbidity and mortality and is clinically characterized by an increase in pulmonary vascular resistance. The histopathology is marked by vascular proliferation/fibrosis, remodeling, and vessel obstruction. Development of PAH involves the complex interaction of multiple vascular effectors at all anatomic levels of the arterial wall. Subsequent vasoconstriction, thrombosis, and inflammation ensue, leading to vessel wall remodeling and cellular hyperproliferation as the hallmarks of severe disease. These processes are influenced by genetic predisposition as well as diverse endogenous and exogenous stimuli. Recent studies have provided a glimpse at certain molecular pathways that contribute to pathogenesis; these have led to the identification of attractive targets for therapeutic intervention. We will review our current understanding of the mechanistic underpinnings of the genetic and exogenous/acquired triggers of PAH. The resulting imbalance of vascular effectors provoking pathogenic vascular changes will also be discussed, with an emphasis on common and overarching regulatory pathways that may relate to the primary triggers of disease. The current conceptual framework should allow for future studies to refine our understanding of the molecular pathogenesis of PAH and improve the therapeutic regimen for this disease.