Different phenotypic outcome due to site-specific phosphorylation in the cancer-associated NQO1 enzyme studied by phosphomimetic mutations

Protein phosphorylation is a common phenomenon in human flavoproteins although the functional consequences of this site-specific modification are largely unknown. Here, we evaluated the effects of site-specific phosphorylation (using phosphomimetic mutations at sites S40, S82 and T128) on multiple functional aspects as well as in the structural stability of the antioxidant and disease-associated human flavoprotein NQO1 using biophysical and biochemical methods. In vitro biophysical studies revealed effects of phosphorylation at different sites such as decreased binding affinity for FAD and structural stability of its binding site (S82), conformational stability (S40 and S82) and reduced catalytic efficiency and functional cooperativity (T128). Local stability measurements by H/D exchange in different ligation states provided structural insight into these effects. Transfection of eukaryotic cells showed that phosphorylation at sites S40 and S82 may reduce steady-levels of NQO1 protein by enhanced proteasome-induced degradation. We show that site-specific phosphorylation of human NQO1 may cause pleiotropic and counterintuitive effects on this multifunctional protein with potential implications for its relationships with human disease. Our approach allows to establish relationships between site-specific phosphorylation, functional and structural stability effects in vitro and inside cells paving the way for more detailed analyses of phosphorylation at the flavoproteome scale.

Allosteric Communication in the Multifunctional and Redox NQO1 Protein Studied by Cavity-Making Mutations

Allosterism is a common phenomenon in protein biochemistry that allows rapid regulation of protein stability; dynamics and function. However, the mechanisms by which allosterism occurs (by mutations or post-translational modifications (PTMs)) may be complex, particularly due to long-range propagation of the perturbation across protein structures. In this work, we have investigated allosteric communication in the multifunctional, cancer-related and antioxidant protein NQO1 by mutating several fully buried leucine residues (L7, L10 and L30) to smaller residues (V, A and G) at sites in the N-terminal domain. In almost all cases, mutated residues were not close to the FAD or the active site. Mutations L→G strongly compromised conformational stability and solubility, and L30A and L30V also notably decreased solubility. The mutation L10A, closer to the FAD binding site, severely decreased FAD binding affinity (≈20 fold vs. WT) through long-range and context-dependent effects. Using a combination of experimental and computational analyses, we show that most of the effects are found in the apo state of the protein, in contrast to other common polymorphisms and PTMs previously characterized in NQO1. The integrated study presented here is a first step towards a detailed structural–functional mapping of the mutational landscape of NQO1, a multifunctional and redox signaling protein of high biomedical relevance.

Structural basis of the pleiotropic and specific phenotypic consequences of missense mutations in the multifunctional NAD(P)H:quinone oxidoreductase 1 and their pharmacological rescue

The multifunctional nature of human flavoproteins is critically linked to their ability to populate multiple conformational states. Ligand binding, post-translational modifications and disease-associated mutations can reshape this functional landscape, although the structure-function relationships of these effects are not well understood. Herein, we characterized the structural and functional consequences of two mutations (the cancer-associated P187S and the phosphomimetic S82D) on different ligation states which are relevant to flavin binding, intracellular stability and catalysis of the disease-associated NQO1 flavoprotein. We found that these mutations affected the stability locally and their effects propagated differently through the protein structure depending both on the nature of the mutation and the ligand bound, showing directional preference from the mutated site and leading to specific phenotypic manifestations in different functional traits (FAD binding, catalysis and inhibition, intracellular stability and pharmacological response to ligands). Our study thus supports that pleitropic effects of disease-causing mutations and phosphorylation events on human flavoproteins may be caused by long-range structural propagation of stability effects to different functional sites that depend on the ligation-state and site-specific perturbations. Our approach can be of general application to investigate these pleiotropic effects at the flavoproteome scale in the absence of high-resolution structural models.

Germ cell desquamation-based testis regression in a seasonal breeder, the Egyptian long-eared hedgehog, Hemiechinus auritus

Testes of seasonally breeding species experience a severe functional regression before the non-breeding period, which implies a substantial mass reduction due to massive germ-cell depletion. Two alternative mechanisms of seasonal germ-cell depletion have been described in mammals, apoptosis and desquamation (sloughing), but their prevalence has not been determined yet due to reduced number of species studied. We performed a morphological, hormonal, and molecular study of the mechanism of seasonal testicular regression in males of the Egyptian long eared-hedgehog (Hemiechinus auritus). Our results show that live, non-apoptotic, germ cells are massively depleted by desquamation during the testis regression process. This is concomitant with both decreased levels of serum testosterone and irregular distribution of the cell-adhesion molecules in the seminiferous epithelium. The inactive testes maintain some meiotic activity as meiosis onset is not halted and spermatocytes die by apoptosis at the pachytene stage. Our data support the notion that apoptosis is not the major testis regression effector in mammals. Instead, desquamation appears to be a common mechanism in this class.

Effect of HMG-CoA Reductase Inhibition on Vascular Smooth Muscle Cells Extracellular Matrix Production: Role of RhoA

Cholesterol-lowering effects apart, statins can improve the endothelial function, stabilize the atherosclerotic plaques, decrease the oxidative stress and inflammation and inhibit the thrombogenic response by means of the inhibition of isoprenoids, which serve as lipid attachments for intracellular signaling molecules. We aimed to evaluate whether the effect of statins on RhoA activity mediate extracellular matrix production, particularly affecting collagen type I, in smooth muscle cells (SMCs). Our results showed that lovastatin decreased collagen expression in primary cultured chicken SMCs as determined by incorporation of [H3]-proline, RT-PCR and immunocytochemistry. This fall was parallel to that found in Rho A activity. Similar results were found when GGTI-298, a RhoA inhibitor, was added to the culture medium. Mevalonate or geranylgeranyl pyrophosphate reverted these effects. In order to elucidate the role of Rho A in these events we transfected the cell line A10 (rat SMCs) with constitutively active (G14V) or dominant negative RhoA (T19N) constructs. The last ones showed similar results regarding collagen production that those stated above in lovastatin treated primary SMC cultures. Constitutively active RhoA transfected cells showed the opposite effects. Next we performed a promoter activity assay to exclude post-transcriptional mechanisms implicated in these studies. We found a similar pattern in col1a2 promoter activity to that found in collagen expression. Our results have demonstrated that statins regulate the activation of RhoA through its isoprenylation, which is crucial for the regulation of extracellular matrix synthesis in SMCs.

Site-to-site interdomain communication may mediate different loss-of-function mechanisms in a cancer-associated NQO1 polymorphism

Disease associated genetic variations often cause intracellular enzyme inactivation, dysregulation and instability. However, allosteric communication of mutational effects to distant functional sites leading to loss-of-function remains poorly understood. We characterize here interdomain site-to-site communication by which a common cancer-associated single nucleotide polymorphism (c.C609T/p.P187S) reduces the activity and stability in vivo of NAD(P)H:quinone oxidoreductase 1 (NQO1). NQO1 is a FAD-dependent, two-domain multifunctional stress protein acting as a Phase II enzyme, activating cancer pro-drugs and stabilizing p53 and p73α oncosuppressors. We show that p.P187S causes structural and dynamic changes communicated to functional sites far from the mutated site, affecting the FAD binding site located at the N-terminal domain (NTD) and accelerating proteasomal degradation through dynamic effects on the C-terminal domain (CTD). Structural protein:protein interaction studies reveal that the cancer-associated polymorphism does not abolish the interaction with p73α, indicating that oncosuppressor destabilization largely mirrors the low intracellular stability of p.P187S. In conclusion, we show how a single disease associated amino acid change may allosterically perturb several functional sites in an oligomeric and multidomain protein. These results have important implications for the understanding of loss-of-function genetic diseases and the identification of novel structural hot spots as targets for pharmacological intervention.

Inhibition of extracellular matrix production and remodeling by doxycycline in smooth muscle cells

Alterations in the extracellular matrix (ECM) production and remodeling of smooth muscle cells (SMCs) have been implicated in processes related to the differentiation in atherosclerosis. Due to the anti-atherosclerotic properties of the tetracyclines, we aimed to investigate whether cholesterol supplementation changes the effect of doxycycline over the ECM proteins synthesis and whether isoprenylated proteins and Rho A protein activation are affected. SMC primary culture isolated from chicks exposed to atherogenic factors in vivo (a cholesterol-rich diet, SMC-Ch), comparing it with control cultures isolated after a standard diet (SMC-C). After treatment with 20 nM doxycycline, [H³]-proline and [H³]-mevalonate incorporation were used to measure the synthesis of collagen and isoprenylated proteins, respectively. Real-time PCR was assessed to determine col1a2, col2a1, col3a1, fibronectin, and mmp2 gene expression and the pull-down technique was applied to determine the Rho A activation state. A higher synthesis of collagens and isoprenylated proteins in SMC-Ch than in SMC-C was determined showing that doxycycline inhibits ECM production and remodeling in both SMC types of cultures. Moreover, preliminary results about the effect of doxycycline on protein isoprenylation and Rho A protein activation led us to discuss the possibility that membrane G-protein activation pathways could mediate the molecular mechanism.

TNFA -308 (rs1800629) polymorphism is associated with a higher risk of cardiovascular disease in patients with rheumatoid arthritis

OBJECTIVE

To assess the influence of the TNFA rs1800629 (G > A) polymorphism in the risk of cardiovascular (CV) disease and subclinical atherosclerosis in patients with rheumatoid arthritis (RA).

METHODS

587 patients fulfilling the 1987 American College of Rheumatology classification criteria for RA were studied. Patients were genotyped for the TNFA rs1800629 polymorphism using predesigned TaqMan single nucleotide polymorphism genotyping assay. Also, HLA-DRB1 genotyping was performed using molecular based methods. Carotid artery intima-media thickness, flow-mediated endothelium-dependent and endothelium independent vasodilatation, used as surrogate markers of subclinical atherosclerosis, were measured in a subgroup of patients.

RESULTS

We observed a higher frequency of carriers of the minor allele A among the patients with CV disease (with 37.6% vs. without 27.9%, p = 0.06, OR 1.56 [95% confidence interval-CI 0.95-2.54]). Carriers of the minor allele A exhibited a higher risk of CV events after adjustment for demographic and traditional CV risk factors (p = 0.023, HR 1.72 [95% CI 1.076-2.74]). Also, a significant interaction between this polymorphism and the presence of the rheumatoid shared epitope (SE) was observed (p = 0.024). Due to this, the association between carriers of the minor allele A and CV disease was only present in carriers of the SE, even after adjustment (p = 0.001, HR 2.43 [95% CI 1.41-4.19]). No significant association between the TNFA variant and the surrogate markers of subclinical atherosclerosis was observed.

CONCLUSION

Our results show that TNFA rs1800629 gene polymorphism is associated with predisposition to CV complications in patients with RA. This predisposition is restricted to individuals carrying the rheumatoid SE.

Association of FcgR2a, but not FcgR3a, with inflammatory bowel diseases across three Caucasian populations

BACKGROUND

The Fc receptors II and III (FcgR2a, and FcgR3a) play a crucial role in the regulation of the immune response. The FcgR2a*519GG and FcgR3a*559CC genotypes have been associated with several autoimmune diseases including systemic lupus erythematosus, rheumatoid arthritis, nephritis, and possibly to type I diabetes, and celiac disease. In a large multicenter, two-stage study of 6570 people, we tested whether the FcgR2a and FcgR3a genes were also involved in inflammatory bowel disease (IBD), which includes Crohn's disease (CD) and ulcerative colitis (UC).

METHODS

We genotyped the FcgR2a*A519G and FcgR3a*A559C functional variants in 4205 IBD patients in six well-phenotyped Caucasian IBD cohorts and 2365 ethnically matched controls recruited from the Netherlands, Spain, and New Zealand.

RESULTS

In the initial Dutch study we found a significant association of FcgR2a genotypes with IBD (P-genotype = 0.02); while the FcgR2a*519GG was more common in controls (23%) than in IBD patients (18%; odds ratio [OR] = 0.75; 95% confidence interval [CI] 0.61-0.92; P = 0.004). This association was corroborated by a combined analysis across all the study populations (Mantel-Haenszel [MH] OR = 0.84; 0.74-0.95; P = 0.005) in the next stage. The Fcgr2a*GG genotype was associated with both UC (MH-OR = 0.84; 0.72-0.97; P = 0.01) and CD (MH-OR = 0.84; 0.73-0.97; P = 0.01), suggesting that this genotype confers a protective effect against IBD. There was no association of FcgR3a*A559C genotypes with IBD, CD, or UC in any of the three studied populations.

CONCLUSIONS

The FcgR2a*519G functional variant was associated with IBD and reduced susceptibility to UC and to CD in Caucasians. There was no association between FcgR3a*5A559C and IBD, CD or UC.

Lack of association of PTPN22, STAT4 and TRAF1/C5 gene polymorphisms with cardiovascular risk in rheumatoid arthritis

OBJECTIVES

To determine whether the PTPN22, STAT4 and TRAF1/C5 gene polymorphisms may be implicated in the development of cardiovascular (CV) events and subclinical atherosclerosis manifested by the presence of endothelial dysfunction or increased carotid intima-media thickness (IMT) in a series of Spanish patients with rheumatoid arthritis (RA).

METHODS

Six hundred and twelve patients fulfilling the 1987 American College of Rheumatology classification criteria for RA, seen at the rheumatology outpatient clinics of Hospital Xeral-Calde, Lugo, and Hospital San Carlos, Madrid, were studied. Patients were genotyped using predesigned TaqMan single nucleotide polymorphism genotyping assays. Moreover, between March and December 2007, a subgroup of unselected RA patients with no history of CV events was studied for the presence of subclinical atherosclerosis by the assessment of the endothelial function (n=126) and the carotid artery IMT (n=110) by ultrasonography studies.

RESULTS

No significant differences in the allele or genotype frequencies for the PTPN22, STAT4 and TRAF1/C5 gene polymorphisms between RA patients with or without CV events were found. It was also the case when we analysed the potential influence of the genotypes in the presence of endothelial dysfunction or increased carotid artery IMT of patients with RA.

CONCLUSIONS

Our results do not show that the PTPN22, STAT4 and TRAF1/C5 gene polymorphisms may confer a direct risk of CV disease in patients with RA.

A1298C polymorphism in the MTHFR gene predisposes to cardiovascular risk in rheumatoid arthritis

INTRODUCTION

We determined the contribution of the methylene tetrahydrofolate reductase (MTHFR) 677 C>T and 1298 A>C gene polymorphisms to the susceptibility to rheumatoid arthritis (RA). We also assessed whether these two MTHFR gene polymorphisms may be implicated in the development of cardiovascular (CV) events and subclinical atherosclerosis manifested by the presence of endothelial dysfunction, in a series of Spanish patients with RA.

METHODS

Six hundred and twelve patients fulfilling the 1987 American College of Rheumatology classification criteria for RA, seen at the rheumatology outpatient clinics of Hospital Xeral-Calde, Lugo and Hospital San Carlos, Madrid, were studied. Patients and controls (n = 865) were genotyped using predesigned TaqMan SNP genotyping assays.

RESULTS

No significant differences in allele or genotype frequencies for the MTHFR gene polymorphisms between RA patients and controls were found. Also, no association between the MTHFR 677 C>T polymorphism and CV events or endothelial dysfunction was observed. However, the MTHFR 1298 allele C frequency was increased in patients with CV events after 5 years (38.7% versus 30.3%; odds ratio = 1.45; 95% confidence interval = 1.00 to 2.10; P = 0.04) and 10 years (42.2% versus 31.0%; odds ratio = 1.62; 95% confidence interval = 1.08 to 2.43; P = 0.01) follow up. Moreover, patients carrying the MTHFR 1298 AC and CC genotypes had a significantly decreased flow-mediated endothelium-dependent vasodilatation (4.3 +/- 3.9%) compared with those carrying the MTHFR 1298 AA genotype (6.5 +/- 4.4%) (P = 0.005).

CONCLUSIONS

Our results show that the MTHFR 1298 A>C gene polymorphism confers an increased risk for subclinical atherosclerosis and CV events in patients with RA.

Genome-wide association study of systemic sclerosis identifies CD247 as a new susceptibility locus

Systemic sclerosis (SSc) is an autoimmune disease characterized by fibrosis of the skin and internal organs that leads to profound disability and premature death. To identify new SSc susceptibility loci, we conducted the first genome-wide association study in a population of European ancestry including a total of 2,296 individuals with SSc and 5,171 controls. Analysis of 279,621 autosomal SNPs followed by replication testing in an independent case-control set of European ancestry (2,753 individuals with SSc (cases) and 4,569 controls) identified a new susceptibility locus for systemic sclerosis at CD247 (1q22-23, rs2056626, P = 2.09 x 10(-7) in the discovery samples, P = 3.39 x 10(-9) in the combined analysis). Additionally, we confirm and firmly establish the role of the MHC (P = 2.31 x 10(-18)), IRF5 (P = 1.86 x 10(-13)) and STAT4 (P = 3.37 x 10(-9)) gene regions as SSc genetic risk factors.

Lack of association between the rs6920220 (G/A) polymorphism of the 6q23 region and biopsy-proven giant cell arteritis

OBJECTIVE

Recently, 2 independent studies have identified an association between several single-nucleotide polymorphisms (SNP) located in the 6q23 chromosomal region and rheumatoid arthritis (RA). Like RA, giant cell arteritis (GCA) is also a complex polygenic disease in which more than 1 genetic locus is likely to contribute to disease susceptibility and clinical expression. We analyzed the involvement of the rs6920220 (G/A) polymorphism from the 6q23/TNFAIP3 gene region in susceptibility to GCA.

METHODS

Two hundred twenty patients with biopsy-proven GCA and 490 matched controls were assessed. DNA from patients and controls was obtained from peripheral blood. Samples were geno-typed for the 6q23 region rs6920220 using a TaqMan allele discrimination assay and by polymerase chain reaction (PCR) amplification. After PCR, the genotype of each sample was attributed automatically by allelic-specific fluorescence using the ABI Prism 7900 sequence detection system.

RESULTS

No significant differences in the genotype distribution between patients with GCA and controls for the rs6920220 (G/A) polymorphism were found. No significant differences were observed when patients with GCA were stratified according to the presence of specific clinical features of the disease such as polymyalgia rheumatica or severe ischemic manifestations or specific visual ischemic complications.

CONCLUSION

Our results show no involvement of this 6q23/TNFAIP3 gene region SNP in the susceptibility to or clinical expression of GCA.

Lack of association between IFNGR1 gene polymorphisms and biopsy-proven giant cell arteritis

OBJECTIVES

Since IFN-gamma plays a pivotal role in the pathogenesis of giant cell arteritis (GCA), a polygenic primary systemic vasculitis involving elderly people from Western countries, in the present study we analysed for first time the implication of three IFN-gamma receptor (IFNGR) 1 gene variants in the susceptibility to and clinical expression of GCA.

METHODS

Two hundred and sixteen biopsy-proven GCA patients and 460 matched controls were assessed. DNA from patients and controls was obtained from peripheral blood. Samples were genotyped for three single nucleotide polymorphisms (SNPs) rs1327474 (-611A/G), rs11914 (+189G7C) and rs7749390 (+95C/T) of the IFNGR1 gene using a pre-designed TaqMan allele discrimination assay. Post PCR, the genotype of each sample was attributed automatically by measuring the allelic specific fluorescence on the ABI PRISM 7900 sequence.

RESULTS

No significant differences in the genotype or allele distribution between GCA patients and controls for the three IFNGR1 gene variants were found. Furthermore, no significant differences in the genotype distribution were observed when GCA patients were stratified according to the presence of specific clinical features of the disease such as polymyalgia rheumatica or severe ischemic complications including visual ischemic manifestations.

CONCLUSIONS

Our results do not show an implication of IFNGR1gene polymorphisms in the susceptibility to and clinical expression of GCA.

Lack of association between macrophage migration inhibitory factor-173 gene polymorphism with disease susceptibility and cardiovascular risk in rheumatoid arthritis patients from northwestern Spain

OBJECTIVES

To assess whether the polymorphism of the macrophage migration inhibitory factor (MIF) gene at the position -173 is implicated in the disease susceptibility, risk of cardiovascular (CV) events and presence of subclinical atherosclerosis in patients with rheumatoid arthritis (RA).

PATIENTS AND METHODS

A series of 293 unselected patients fulfilling the 1987 American College of Rheumatology classification criteria for RA seen at the rheumatology outpatient clinic of Hospital Xeral-Calde, Lugo, Spain and 526 matched controls were studied for differences in the MIF-173 G/C gene biallelic polymorphism. A total of 182 consecutive patients that had been periodically followed between March 1996 and September 1996 until patient's death or January 1, 2008 were assessed for the presence of CV events. Moreover, between March and December 2007, a subgroup of unselected RA patients with no history of CV events was studied for the presence of subclinical atherosclerosis by the assessment of the endothelial function (n=107) and the carotid artery intima-media thickness (IMT) (n=91) by ultrasonography studies. Patients and controls were genotyped for the MIF-173 G/C gene polymorphism using a PCR system with pre-developed TaqMan allelic discrimination assay.

RESULTS

No significant differences in allele or genotype frequencies for the MIF-173 gene polymorphism between RA patients and controls were found. Forty-four of the 182 patients followed between 1996 and January 2008 experienced CV events. Although the frequency of MIF-173 GG homozygous was increased in those who had CV events (88.6%) compared to those who did not suffer these complication (73.2%), the difference was not statistically significant. It was also the case when we analyzed the potential influence of MIF-173 genotypes in the presence of endothelial dysfunction or increased carotid IMT of patients with RA.

CONCLUSIONS

Our results do not show that MIF-173 gene polymorphism may infer a direct risk for disease susceptibility or CV disease in patients with RA.

Lack of association between hypoxia inducible factor-1 alpha gene polymorphisms and biopsy-proven giant cell arteritis

OBJECTIVES

Since the transcription factor hypoxia-inducible factor 1 (HIF-1) is a key early mediator of the response to ischemia and giant cell arteritis (GCA) is a polygenic disease leading to severe ischemic complications, in the present study we analysed for first time the implication of two HIF-1alpha gene polymorphisms in the susceptibility to and clinical expression of GCA.

METHODS

Two hundred and fifteen biopsy-proven GCA patients and 470 matched controls were assessed. DNA from patients and controls was obtained from peripheral blood. Samples were genotyped for two single nucleotide polymorphisms, rs11549465 (C/T) and rs11549467 (G/A), using a pre-designed TaqMan allele discrimination assay. Post PCR, the genotype of each sample was attributed automatically by measuring the allelic specific fluorescence on the ABI PRIM 7900 sequence.

RESULTS

The HIF-1alpha, rs11549465 TT genotype was extremely uncommon in both GCA patients (2.3%) and controls (2.1%). Although the frequency of individuals carrying the CT or TT genotypes was increased in GCA patients (25.1%) compared to controls (20.4%) the difference was not statistically significant (OR 1.30 [95% CI: 0.89- 1.91]; p=0.17). Also, all GCA patients and most controls (98.9%) were homozygous for the rs11549467 GG genotype. GCA patients carrying the rs11549465 CT or TT genotypes had a slight increased risk of developing visual ischemic complications (33.1%) compared to the remaining GCA patients (22.8%); OR 1.60 (95% CI: 0.81- 3.16); p=0.18.

CONCLUSIONS

Our results do not confirm an implication of HIF-1alpha gene polymorphisms in the susceptibility to and clinical expression of GCA.

Influence of cholesterol and fish oil dietary intake on nitric oxide-induced apoptosis in vascular smooth muscle cells

Apoptosis of vascular smooth muscle cells (SMC) is critically involved in the progression of atherosclerosis. We previously reported that dietary cholesterol intake induces changes in SMC at molecular and gene expression levels. The objectives of the present study were to investigate the differential response to nitric oxide of vascular SMC obtained from chicks after cholesterol and fish oil dietary intake and to examine effects on the main pro-apoptotic and anti-apoptotic genes. Dietary cholesterol intake reduced the Bcl-2/Bax (anti-apoptotic/pro-apoptotic) protein ratio in SMC, making them more susceptible to apoptosis. When cholesterol was withdrawn and replaced with a fish oil-enriched diet, the Bcl-xl/Bax protein ratio significantly increased, reversing the changes induced by cholesterol. The decrease in c-myc gene expression after apoptotic stimuli and the increase in Bcl-xl/Bax ratio indicate that fish oil has a protective role against apoptosis in SMC. Nitroprussiate-like nitric oxide donors exerted an intensive action on vascular SMC cultures. However, SMC-C (isolated from animals fed with control diet) and SMC-Ch (isolated from animals fed with cholesterol-enriched diet) responded differently to nitric oxide, especially in their bcl-2 and bcl-xl gene expression. SMC isolated from animals fed with cholesterol-enriched and then fish oil-enriched diet (SMC-Ch-FO cultures) showed an intermediate apoptosis level (Bcl-2/Bax ratio) between SMC-C and SMC-Ch, induction of c-myc expression and elevated p53 expression. These findings indicate that fish oil protects SMC against apoptosis.

Interleukin-6 gene -174 promoter polymorphism is associated with endothelial dysfunction but not with disease susceptibility in patients with rheumatoid arthritis

OBJECTIVE

To determine whether the interleukin (IL)6 -174 gene polymorphism may influence the development of subclinical atherosclerosis manifested by the presence of endothelial dysfunction in RA patients.

PATIENTS AND METHODS

311 patients (228 [73.3%] women; 243 [78.1%] rheumatoid factor positive) who fulfilled the 1987 ACR classification criteria for RA seen at the Rheumatology outpatient clinic of Hospital Xeral-Calde, Lugo between March 1996 and December 2006 and 226 matched controls were included in this study. Between March and December 2007, a subgroup of 98 patients randomly selected was assessed for the presence of endothelial dysfunction. Patients and controls were genotyped for a single biallelic (G/C) nucleotide polymorphism (rs1800795) in the promoter region at the position -174 of the IL6 gene using a TaqMan 5' allele discrimination assay.

RESULTS

No significant differences in the IL6 -174 allele or genotype frequency between RA patients and controls were found. However, RA patients homozygous for the IL6 -174 GG genotype had more severe endothelial dysfunction (flow-mediated endothelium-dependent vasodilatation-FMD%: 4.2 + or - 6.6) than those carrying the IL6 -174 GC (FMD%: 6.3 + or - 8.1) or IL6 -174 CC (FMD%: 6.0 + or - 3.3) genotypes. In this regard, significant differences were observed when FMD% values in RA patients carrying the IL6 -174 GG genotype were compared with that observed in those carrying the IL6 -174 GC and the IL6 -174 CC genotypes (FMD%: 6.3 + or - 4.6) (p=0.02).

CONCLUSIONS

Our results support a role of IL6 -174 gene polymorphism in the development of subclinical atherosclerosis in patients with RA.

Novel association of the interleukin 2-interleukin 21 region with inflammatory bowel disease

OBJECTIVES

Genome-wide association studies have reported the role of the interleukin (IL) 2-IL21 chromosomal region at 4q27 in several autoimmune conditions. Mice deficient in IL-2 develop a disease with clinical and histological similarity to ulcerative colitis (UC) in humans. Modest evidence of linkage with UC was tentatively proposed for the IL2 gene more than a decade ago. Therefore, we decide to investigate the association of polymorphisms in the IL-2 axis (IL2, IL2RA, and IL2RB genes) with inflammatory bowel diseases (IBDs).

METHODS

Seven hundred and twenty-eight white Spanish unrelated IBD patients (356 Crohn's disease (CD) and 372 UC) and 549 ethnically matched controls were included in a case-control study. In addition, a Spanish replication cohort with 562 CD and 430 UC patients and 1,310 controls were analyzed. Eight single-nucleotide polymorphisms previously associated with different autoimmune diseases were analyzed using TaqMan chemistry.

RESULTS

The IL2-rs6822844 polymorphism modified CD predisposition (P=0.002; odds ratio, OR (95% confidence interval, CI)=0.61 (0.44-0.84)); this was replicated in the other Spanish cohort, resulting in a strong protective effect of the minor allele in the merged samples (P=0.0002; OR (95% CI)=0.70 (0.58-0.85)). A similar effect of rs6822844 was detected for UC. Another marker, rs11938795, also showed evidence of an association with CD (P=0.006; OR (95% CI)=0.73 (0.58-0.92)).

CONCLUSIONS

Polymorphisms within the IL2-IL21 linkage disequilibrium (LD) block show a novel association with IBD, this is concordant with suggestive previous results of whole genome analyses in CD and type 1 diabetes. Our data agree with the effect previously observed for other conditions and delineate a shared underlying mechanism.

Influence of nitric oxide synthase gene polymorphisms on the risk of cardiovascular events in rheumatoid arthritis

OBJECTIVE

Complex interactions between environmental and genetic determinants in both the host immune system and the vasculature may operate modifying the vascular risk in rheumatoid arthritis (RA). An increased incidence of cardiovascular (CV) events in RA patients carrying HLA-DRB1 shared epitope alleles, in particular HLA-DRB1*0404, has recently been found. In the present study we have assessed the potential contribution of inducible and endothelial nitric oxide synthase (NOS2A and NOS3) gene polymorphisms to CV events in a cohort of patients with rheumatoid arthritis (RA). Also, interactions between NOS2A or NOS3 gene polymorphisms and HLA-DRB1 alleles for the risk of developing CV events were assessed.

PATIENTS AND METHODS

One hundred and eighty-two consecutive patients fulfilling the 1987 American College of Rheumatology classification criteria for RA seen at the Rheumatology outpatient clinic of Hospital Xeral Calde, Lugo, Northwest Spain, between March and September 1996 were included. Patients were genotyped by PCR based techniques for a multiallelic (CCTTT)n repeat 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 or 5557G/T) of the NOS3 gene. They were prospectively followed and clinical records were examined until patient's death or September 1, 2005. At the end of the study 39 (21%) patients had experienced CV events.

RESULTS

No significant differences in allele or genotype frequencies for the NOS2A promoter CCTTT repeat microsatellite and NOS3 gene polymorphisms between RA patients with or without CV events were found. However, an increased frequency of CV events was observed in RA patients who carried the HLA-DRB1*0404 allele and were homozygous for the NOS3 (-786) TT genotype (OR: 9.06 [95% CI: 1.29-63.37]; p= 0.03) or for the presence of long NOS2A alleles (OR: 11.7 [95% CI: 1.53-88.4]); p= 0.02).

CONCLUSIONS

Our results show that NOS2A or NOS3 gene polymorphisms do not infer a direct risk for CV events in RA. However, some interactions between NOS gene polymorphisms and HLA-DRB1 alleles confer and increased risk of developing CV events in patients with RA.

Cyclic fluctuations of 3-hydroxy-3-methylglutaryl-CoA reductase in aortic smooth muscle cell cultures

The cyclic fluctuations of HMG-CoA reductase activity and mRNA are reportedly related to feeding the cells in culture or to variations in food consumption by the animals over a 24-h cycle. In this work, we demonstrate cyclic increments in HMG-CoA reductase activity in smooth muscle cells (SMC) not associated with the culture feeding. Since reductase activity also shows a marked rise preceding the S phase, one of the major goals of the present work was to evaluate this dual role of reductase activity and mRNA fluctuations related to the cell cycle and to food intake in the SMC-C/SMC-Ch cultures derived from control-fed (SMC-C) and cholesterol-fed (SMC-Ch) chicks. The period and amplitude oscillations in HMG-CoA reductase activity varied depending on culture conditions: lipoprotein-deficient serum vs. FBS, young vs. senescent cells, or confluent vs. nonconfluent cultures. The HMG-CoA reductase mRNA concentration showed a marked rise after feeding not correlated to the fluctuation activity, suggesting posttranscriptional modulation. Reductase activity and mRNA were down-regulated in SMC-Ch. Since the nutritional culture conditions were the same in both cell lines, these findings indicate that consumption of a high-cholesterol diet by the animals prior to the establishment of the SMC cultures induced changes in the HMG-CoA reductase gene expression in-aortic SMC.