The -174/-597 promoter polymorphisms in the interleukin-6 gene are not associated with susceptibility to multiple sclerosis

Therapeutic effects of pegylated-interferon-α2a in a mouse model of multiple sclerosis

Introduction

Experimental autoimmune encephalomyelitis (EAE) is an animal model of multiple sclerosis (MS). EAE is mainly mediated by adaptive and innate immune responses that lead to an inflammatory demyelination and axonal damage. The aim of the present research was to examine the therapeutic efficacy of Peg interferon alpha 2a (Peg-IFN α-2a) as a serine protease inhibitor on EAE model.

Material and methods

EAE induction was performed in female C57BL/6 mice by myelin oligodendrocyte glycoprotein (35-55) (MOG_35-55) in Complete Freund’s Adjuvant (CFA) emulsion, and Peg-IFN α-2a was used for the treatment of EAE. During the course of the study, clinical evaluation was assessed, and on day 21 post-immunisation blood samples were taken from the heart of mice for evaluation of IL-6, and enzymatic and non-enzymatic antioxidants. The mice were sacrificed and the brains and cerebellums were removed for histological analysis.

Results

Our findings indicated that Peg-IFN α-2a had beneficial effects on EAE by attenuation of the severity and a delay in the onset of disease. Histological analysis showed that treatment with Peg-IFN α-2a can reduce inflammation criteria. Moreover, in Peg-IFN α-2a-treated mice the serum level of IL-6 was significantly less than in controls, and total antioxidant capacity was significantly more than in the control animals.

Conclusions

These data indicate that Peg-IFN α-2a as an anti-serine protease with immunomodulatory properties may be useful for the treatment of MS.

Interleukin-6, a major cytokine in the central nervous system

Interleukin-6 (IL-6) is a cytokine originally identified almost 30 years ago as a B-cell differentiation factor, capable of inducing the maturation of B cells into antibody-producing cells. As with many other cytokines, it was soon realized that IL-6 was not a factor only involved in the immune response, but with many critical roles in major physiological systems including the nervous system. IL-6 is now known to participate in neurogenesis (influencing both neurons and glial cells), and in the response of mature neurons and glial cells in normal conditions and following a wide arrange of injury models. In many respects, IL-6 behaves in a neurotrophin-like fashion, and seemingly makes understandable why the cytokine family that it belongs to is known as neuropoietins. Its expression is affected in several of the main brain diseases, and animal models strongly suggest that IL-6 could have a role in the observed neuropathology and that therefore it is a clear target of strategic therapies.

Interleukin-6 gene promoter-572 C allele may play a role in rate of disease progression in multiple sclerosis

Multiple sclerosis (MS) is an inflammatory demyelinating disease affecting the central nervous system. Although the exact pathogenesis of MS is unknown, it is generally considered to be an autoimmune disease, with numerous genetic and environmental factors determining disease susceptibility and severity. One important mediator of immune responses and inflammation is interleukin-6 (IL-6). Previously, elevated levels of IL-6 in mononuclear cells in blood and in brain tissue from MS patients have been reported. Various polymorphisms in the promoter region of the IL6 gene have also been linked with IL-6 protein levels. In MS, several small studies have investigated whether two IL6 promoter polymorphisms (−597 G>A and −174 G>C) correlate with MS susceptibility, but with varying results. In the present study, we analyzed these polymorphisms, together with an additional polymorphism (−572 G>C) in 279 healthy controls and 509 patients with MS. We found no significant differences between MS patients and healthy controls for the different −597 or −174 IL6 promoter alleles or genotypes. There was a slight reduction in the percentage of individuals with MS who carried a C allele at position −572, although this was not significant after correction for multiple comparisons. Interestingly, however, the −572 C allele showed a significant correlation with the MS severity score, suggesting a possible role in disease progression.

Interleukin-6, a mental cytokine

Almost a quarter of a century ago, interleukin-6 (IL-6) was discovered as an inflammatory cytokine involved in B cell differentiation. Today, IL-6 is recognized to be a highly versatile cytokine, with pleiotropic actions not only in immune cells, but also in other cell types, such as cells of the central nervous system (CNS). The first evidence implicating IL-6 in brain-related processes originated from its dysregulated expression in several neurological disorders such as multiple sclerosis, Alzheimer's disease and Parkinson's disease. In addition, IL-6 was shown to be involved in multiple physiological CNS processes such as neuron homeostasis, astrogliogenesis and neuronal differentiation. The molecular mechanisms underlying IL-6 functions in the brain have only recently started to emerge. In this review, an overview of the latest discoveries concerning the actions of IL-6 in the nervous system is provided. The central position of IL-6 in the neuroinflammatory reaction pattern, and more specifically, the role of IL-6 in specific neurodegenerative processes, which accompany Alzheimer's disease, multiple sclerosis and excitotoxicity, are discussed. It is evident that IL-6 has a dichotomic action in the CNS, displaying neurotrophic properties on the one hand, and detrimental actions on the other. This is in agreement with its central role in neuroinflammation, which evolved as a beneficial process, aimed at maintaining tissue homeostasis, but which can become malignant when exaggerated. In this perspective, it is not surprising that 'well-meant' actions of IL-6 are often causing harm instead of leading to recovery.

HLA-DRB1*1501 intensifies the impact of IL-6 promoter polymorphism on the susceptibility to multiple sclerosis in an Iranian population

Background: The multifunctional cytokine interleukin-6 (IL-6) is involved in inflammatory processes in the central nervous system. It is well documented that amount of IL-6 is increased in serum, cerebrospinal fluid and central nervous system lesions of patients with multiple sclerosis. A single nucleotide polymorphism at position -174 in the IL-6 gene promotor appears to influence IL-6 expression. Recently, several researchers have focused on HLA-DRB alleles, specifically HLA-DRB1*1501, as a potential risk allele in the pathogenesis of multiple sclerosis.

Objective: To investigate the possible influence of IL-6/-174 polymorphisms on susceptibility to multiple sclerosis and its integration with HLA-DRB1*1501. Genomic DNA was extracted from whole blood of 345 patients with multiple sclerosis and 426 control subjects.

Method: The SSP-PCR method was used to determine genotypes and Fisher’s exact test was applied to determine differences between groups. HLA-DRB1*1501 was observed more frequently among multiple sclerosis patients compared with healthy subjects (45% and 34%, respectively; OR = 1.6, 95% CI = 1.2—2.2, p = 0.0018). At the IL-6/-174 position, the G allele had higher frequency among multiple sclerosis patients compared with controls (77% and 70%, respectively; OR = 1.4, 95% CI = 1.1—1.8, p = 0.0038). This difference was more significant among HLA-DRB1*1501-positive patients and controls (81% and 67%, respectively; OR = 1.9, 95% CI = 1.5—2.5, p < 0.0001).

Results: Our results have shown that the G allele at the IL-6/-174 promoter polymorphism may be associated with development of multiple sclerosis in this population, and may be strengthened by HLA-DRB1*1501.

Conclusions: We suggest more studies to confirm these results in other populations.

Polymorphism in interleukin-6 gene is associated with bone mineral density in patients with adolescent idiopathic scoliosis

Low bone mass and osteopenia have been described in the axial and peripheral skeleton of patients with adolescent idiopathic scoliosis (AIS). Recently, many studies have shown that gene polymorphism is related to osteoporosis. However, no studies have linked the association between IL6 gene polymorphism and bone mass in AIS. This study examined the association between bone mass and IL6 gene polymorphism in 198 girls with AIS. The polymorphisms of IL6-597 G→A, IL6-572 G→C and IL6-174 G→A and the bone mineral density in the lumbar spine and femoral neck were analysed and compared with their levels in healthy controls. The mean bone mineral density at both sites in patients with AIS was decreased compared with controls (p = 0.0022 and p = 0.0013, respectively). Comparison of genotype frequencies between AIS and healthy controls revealed a statistically significant difference in IL6-572 G→C polymorphism (p = 0.0305). There was a significant association between the IL6-572 G→C polymorphism and bone mineral density in the lumbar spine, with the CC genotype significantly higher with the GC (p = 0.0124) or GG (p = 0.0066) genotypes.

These results suggest that the IL6-572 G→C polymorphism is associated with bone mineral density in the lumbar spine in Korean girls with AIS.

The genetics of clinical outcome in multiple sclerosis

Multiple sclerosis (MS) is a common inflammatory disease of the central nervous system (CNS), the clinical course of which varies considerably between patients. Genetic complexity and interactions with as yet unknown environmental factors have hindered researchers from fully elucidating the aetiology of the disease. In addition to influencing disease susceptibility, epidemiological evidence suggests that genetic factors may affect phenotypic expression of the disease. Genes that affect clinical outcome may be more effective therapeutic targets than those which determine susceptibility. We present in this review a comprehensive survey of the genes (both MHC- and non-MHC-related) that have been investigated for their role in disease outcome in MS. Recent studies implicating the role of the genotype and epistatic interactions in the MHC in determining outcome are highlighted.

The IL - 6 promoter polymorphism is associated with disease activity and disability in systemic sclerosis

Systemic sclerosis (SSc) is a rare, autoimmune disease characterized by cutaneous and visceral fibrosis. Interleukin-6 (IL-6) is involved in the pathogenesis of many immune-mediated diseases. IL-6 plays an important role in the initiation and promotion of fibrosis. The polymorphism in the position -174 (G/C) of the promoter region of the IL-6 gene (IL-6 pr) may alter the expression of the gene. Complete linkage disequilibrium was observed between the -174 and -597 alleles. The aim of this study is to investigate the possible influence of -597 (-174) IL-6 pr polymorphism on the susceptibility and/or the clinical course of SSc in Romanian population. Genotyping of -597 variant was performed by an RFLP method on 20 SSc patients and 26 healthy subjects. Patients having the homozygous GG (-597) genotype had higher disease activity and disability scores than heterozygous GA patients: the European Scleroderma Study Group (EScSG) disease activity score was 5.0 ± 3.3 in homozygous GG subjects vs. 2.4 ± 3.6 in heterozygous GA patients (p < 0.05), and the Disability Index of the Health Assessment Questionnaire (HAQ-DI) was 1.42 ± 1.04 in homozygous GG subjects vs. 0.53 ± 0.55 in heterozygous GA patients (p < 0.05). No difference was observed in the distribution of allele frequencies between SSc patients and healthy controls. Conclusions: The GG homozygosis was found to be associated with a higher degree of illness activity and disability in SSc patients. No statistically significant differences were found between SSc patients and healthy controls with respect to the -597 allele distribution.

The IL - 6 promoter polymorphism is associated with disease activity and disability in systemic sclerosis

Systemic sclerosis (SSc) is a rare, autoimmune disease characterized by cutaneous and visceral fibrosis. Interleukin- 6 (IL-6) is involved in the pathogenesis of many immune-mediated diseases. IL-6 plays an important role in the initiation and promotion of fibrosis. The polymorphism in the position -174 (G/C) of the promoter region of the IL-6 gene (IL-6pr) may alter the expression of the gene. Complete linkage disequilibrium was observed between the -174 and -597 alleles. The aim of this study is to investigate the possible influence of -597 (-174) IL-6pr polymorphism on the susceptibility and/or the clinical course of SSc in Romanian population. Genotyping of -597 variant was performed by an RFLP method on 20 SSc patients and 26 healthy subjects. Patients having the homozygous GG (-597) genotype had higher disease activity and disability scores than heterozygous GA patients: the European Scleroderma Study Group (EScSG) disease activity score was 5.0 +/- 3.3 in homozygous GG subjects vs. 2.4 +/- 3.6 in heterozygous GA patients (p < 0.05), and the Disability Index of the Health Assessment Questionnaire (HAQ-DI) was 1.42 +/- 1.04 in homozygous GG subjects vs. 0.53 +/- 0.55 in heterozygous GA patients (p < 0.05). No difference was observed in the distribution of allele frequencies between SSc patients and healthy controls.

CONCLUSIONS

The GG homozygosis was found to be associated with a higher degree of illness activity and disability in SSc patients. No statistically significant differences were found between SSc patients and healthy controls with respect to the -597 allele distribution.

Genetic and clinical factors influence the baseline permeability of the peritoneal membrane

BACKGROUND

Patients starting peritoneal dialysis (PD) show a significant variability in small solute transport across the peritoneal membrane (PM). The latter parameter determines dialysis prescription and survival. Clinical factors probably influence solute transport across the PM, but the putative role of genetic variants is unknown.

METHODS

We have investigated the influence of functional polymorphisms of VEGF, ENOS, and IL-6, together with clinical and biological factors, on baseline peritoneal equilibration test (PET) parameters in a homogeneous population of 152 unrelated Caucasian PD patients from Belgium and the North of France.

RESULTS

The distribution of the 21 alleles (7 polymorphisms) and linkage disequilibrium parameters were similar in PD patients and healthy subjects. Univariate and multivariate analyses identified comorbidity, serum albumin, and the -174G/C polymorphism of IL-6 as independent predictors of small solute transport. The -174G/C polymorphism of IL-6 was associated with significantly higher IL-6 mRNA levels in the PM and higher plasma and dialysate IL-6 concentrations, suggesting a dominant effect of the C allele. Patients harboring the CC and GC genotypes (N= 92) were characterized by significantly higher permeability parameters and inflammatory markers than patients harboring the GG genotype (N= 60). In contrast with IL-6, VEGF and ENOS polymorphisms had no influence on baseline peritoneal permeability.

CONCLUSION

These data (1) show that, together with clinical parameters, the functionally relevant -174G/C polymorphism of IL-6 contributes to the interpatient variability in small solute transport rate at the start of PD; and (2) substantiate the critical role played by IL-6 in the PM.

A common interleukin-6 gene promoter polymorphism influences the clinical characteristics of women with polycystic ovary syndrome

OBJECTIVE

To investigate the association of a common polymorphism of the interleukin-6 gene (IL6) promoter with the occurence and the clinical characteristics of polycystic ovary syndrome (PCOS).

DESIGN

Prospective, case-control study.

SETTING

Academic research institution.

PATIENT(S)

Sixty-two patients with PCOS and 94 healthy controls.

INTERVENTION(S)

Peripheral venous puncture, ultrasonography, oral glucose tolerance test (OGTT), questionnaire.

MAIN OUTCOME MEASURE(S)

Genotype analysis with respect to the common -174 G/C polymorphism of the IL6 gene promoter, analysis of testosterone (T), androstendione, and sex hormone binding globulin serum levels, and evaluation of the OGTT.

RESULT(S)

Allele frequencies among women with PCOS and controls were 62.9% and 64.4%, respectively, for the wild-type G allele, and 37.1% and 35.6%, respectively, for the mutant C allele. We ascertained a significant association between presence of at least one mutant C allele and the clinical characteristics of affected women: these women were more likely to present with a body mass index >27 kg/m(2), elevated total T serum levels, and a pathological OGTT result.

CONCLUSION(S)

A common polymorphism of the IL6 promoter, although not associated with the presence of PCOS, is associated with the clinical characteristics of women affected by this condition.

Association of interleukin-6 promoter variant with bone mineral density in pre-menopausal women

Interleukin-6 (IL6) has many roles essential to the regulation of the immune response, hematopoiesis, and bone resorption. Three single-nucleotide polymorphisms (SNP) in the IL6 promoter region were genotyped by the single-base extension method. The frequencies of each SNP were 0.002 ( IL6-597 G--> A), 0.27 ( IL6-572 G--> C), and 0.002 ( IL6-174 G--> C) in a Korean population ( n=1,082). IL6-597 G--> A and IL6-174 G--> C were totally linked together ( d(2)=1) and showed very low allele frequencies (0.002), which are common in Caucasians. On the other hand, the frequency of the IL6-572 G--> C*C allele was much higher (0.27) than that in Caucasian populations (<0.07). One of the IL6 promoter SNPs, viz., IL6-572 G--> C, showed significant associations with bone mineral density (BMD), i.e., the C allele was associated with increased BMD ( P=0.02, co-dominant model; P=0.007, dominant model). The mean BMD was highest in homozygous C individuals (0.67+/-0.15), lowest in homozygous G individuals (0.58+/-0.19), and intermediate in heterozygotes (0.64+/-0.21). In the present study, we describe a variant in the IL6 promoter region that shows positive association with higher BMD in a gene-dose-dependent manner in pre-menopausal women.

Methodologic quality and genotyping reproducibility in studies of tumor necrosis factor -308 G-->A single nucleotide polymorphism and bacterial sepsis: implications for studies of complex traits

OBJECTIVE

Studies of genetic associations with common diseases, such as between cytokine gene polymorphisms and severe bacterial sepsis, have reached conflicting conclusions. Failure to follow methodologic standards may have contributed to discordant findings. The -308 G-->A transition in the tumor necrosis factor-alpha promoter has been genotyped by a variety of methods. Based on our observation of genotyping inaccuracies, we sought to determine whether published studies followed a series of acceptable methodologic standards and whether failure to follow the standard of genotyping reproducibility could lead to erroneous conclusions about gene-disease associations.

DESIGN

Systematic review and reanalysis of banked genetic material. We applied a published series of seven methodologic standards to five reports of the association between this variant and bacterial sepsis. We then studied the accuracy of restriction fragment length polymorphism for the -308 site using DNA from a cohort of injury victims.

SETTING

Surgery research laboratory.

MEASUREMENTS AND MAIN RESULTS

We observed that methodologic quality was not uniform and that reproducibility of genotyping was infrequently met. In our subjects, we found that 4 of 46 heterozygotes analyzed by restriction fragment length polymorphism were actually GG-homozygotes (9% misclassified) according to alternative genotyping methods.

CONCLUSIONS

Failure to confirm genotype may have led to conclusions that this polymorphism is not associated with sepsis or outcome. Our observations have implications for the conduct and evaluation of studies of complex genetic disease.