Lack of an association between interleukin-6 -174G/C polymorphism and circulating interleukin-6 levels in normal population: a meta-analysis

Association between interleukin-6-174G/C gene polymorphism and asthma severity: exploring the role of total serum IgE, blood eosinophils, and FeNO as markers of type 2 inflammation

BACKGROUND

While a connection has been established between serum interleukin-6 (IL-6) levels and the IL-6 gene (- 174G/C) polymorphism in allergic diseases such as asthma, its specific association with severe asthma remains unexplored. This study examined the relationship between the IL-6 (- 174G/C) gene polymorphism and mild and severe asthma, focusing on its influence on type 2 inflammation.

METHODS

Our study comprised 98 patients with mild asthma and 116 with severe asthma. Additionally, we recruited 121 healthy participants to serve as controls for comparative analyses. The IL-6 gene (- 174G/C) polymorphism was assessed utilizing the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method.

RESULTS

In our study, the risk of mild asthma exhibited a significant fourfold increase in individuals with the GG genotype pattern compared to healthy controls, yielding an odds ratio (OR) of 4.4 (p < 0.001). Conversely, we found no significant correlation between the IL-6 - 174G/C gene polymorphism and severe asthma when compared to the healthy control group. However, a noteworthy pattern emerged when we compared subgroups of mild and severe asthma. The risk of severe asthma increased fivefold in individuals with the GC polymorphism pattern, with an OR of 4.99 (p < 0.001), while the likelihood of mild asthma showed a similar fourfold increase with the GG polymorphism pattern, OR = 4.4 (p < 0.001). Consequently, we observed a significantly higher frequency of the C allele in patients with severe asthma, whereas the G allele was more prevalent in individuals with mild asthma (p = 0.05). Additionally, the correlation between markers of type 2 inflammation and the dominant model of the IL-6 gene -174G/C polymorphism (CC + CG vs GG) revealed a significant increase in total serum immunoglobulin E (IgE), Blood Eosinophil Counts (BEC), and Fractional Exhaled Nitric Oxide (FeNO) levels in asthmatic patients with the CC + CG gene pattern compared to those with GG, with p-values of 0.04, 0.03, and 0.04, respectively. Furthermore, after adjusting for other risk factors, the likelihood of developing severe asthma increased from fourfold to eightfold, with an OR of 8.12 (p = 0.01) with (CC + CG) gene pattern. Other predictors for severe asthma included older age and childhood-onset disease (OR = 1.13 and 19.19, p < 0.001). Allergic rhinitis (AR) and nasal polyps (NP) also demonstrated a substantial association with an increased risk of severe asthma, with odds ratios of 5 and 32.29 (p = 0.01 and < 0.001), respectively. Additionally, elevated Body Mass Index (BMI), BEC, and FeNO were linked to severe asthma, with ORs of 1.11, 1.00, and 1.04, respectively (p = 0.04, 0.05, and 0.001).

CONCLUSION

This study illuminated the intricate relationship between the IL-6 gene polymorphism, type 2 inflammation markers, and diverse risk factors in shaping asthma severity. As a significant association between the GG polymorphism of the IL-6 gene (- 174G/C) and mild asthma was found, while possessing at least one C allele, whether in a homozygous (CC) or heterozygous (CG) combination, independently predicts the likelihood of severe asthma.

Interleukin-6 gene -174G>C promoter polymorphism reduces the risk of periodontitis in Brazilian populations: A meta-analysis

INTRODUCTION

Periodontitis is a multifactorial host-mediated oral disease caused by microbes. Previous studies suggested that interleukin-6 (IL-6) gene promoter polymorphism (-174G > C) are associated with the risk of periodontitis, although the results were inconclusive. This study investigated the association between IL-6 -174G > C polymorphism and susceptibility to periodontitis.

METHOD

A comprehensive search was conducted in PubMed, EMBASE, Web of Science, and Google Scholar databases to retrieve relevant studies. Pooled odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to assess the strength of the association between 174G > C polymorphism and the risk of periodontitis. Cochrane Q and I² statistics were used to measure heterogeneity between studies. Publication bias was estimated using Begg's funnel plots and Egger's test.

RESULTS

Our results showed significant differences in the allelic (C vs. G: OR = 0.82, CI = 0.65-1.03), recessive (CC vs. GC + GG: OR = 0.69, CI = 0.42-1.13), and dominant (GC + CC vs. GG: OR = 0.85, CI = 0.63-1.13) genetic models of the IL6 -174G > C polymorphism and risk of periodontitis. Further, subgroup analysis showed decreased susceptibility to periodontitis associated with IL6 -174 G > C in a Brazilian population (C vs. G: OR = 0.60, CI = 0.41-0.88; GC + CC vs. GG: OR = 0.57, CI = 0.42-0.78) but not in Asian or Caucasian populations.

CONCLUSION

The findings of this study revealed that the IL6 -174 "C" allele is protective against periodontitis in the Brazilian population.

Regulation of interleukin 6 by a polymorphic CpG within the frontal cortex in Alzheimer's disease

The cytokine interleukin 6 (IL-6) has been linked to the pathogenesis of Alzheimer's disease (AD). This is the first study to investigate the genetic and epigenetic interactions in the control of IL-6 in human brain and its relation to AD neuropathology in prefrontal cortex tissues from AD and controls genotyped for the SNP -174 C/G rs1800795, a polymorphic CpG in which the G allele creates a CpG site. Within CC homozygotes there were significantly higher brain levels of IL-6 protein compared to G allele carriers. The C allele that resulted in an absence of methylation at a CpG was also associated with significant changes in methylation at neighboring CpGs. Furthermore, there were significant differences in methylation between CC and CG/GG at CpG sites in the AD and control groups. That DNA methylation was altered in the brains by the presence of rs1800795, which further correlated with protein levels suggests the presence of a polymorphic CpG and genetic-epigenetic interactions in the regulation of IL-6 in the prefrontal cortex within AD brains.

Association between rs1800795 polymorphisms in the interleukin-6 gene and vasculitis: A meta-analysis

Interleukin (IL)-6 is associated with the development and progression of vasculitis, and inhibitors of this cytokine are used to treat this disease. Polymorphisms of the promoter region of IL-6 are associated with the production and expression of IL-6. The aim of this study was to perform a meta-analysis of eligible studies to derive a precise estimate of the association between IL6 polymorphisms and susceptibility to vasculitis. A meta-analysis was conducted to identify the associations between IL6 rs1800795 (-174 G/C) polymorphisms and vasculitis. A total of 13 studies involving 1,294 vasculitis patients and 1,594 controls were considered in the meta-analysis. There were significant associations between IL6 rs1800795 polymorphisms and vasculitis in allele contrast, dominant genetic model, and heterozygote vs. dominant homozygote comparison (OR 0.80, 95% CI 0.67-0.94, P =0.009 and OR 0.76, 95% CI 0.63-0.92, P =0.005, respectively). In subgroup analysis based on subtype, there were significant associations between IL6 polymorphisms and susceptibility in large and medium vessel vasculitis, but not in small and variable vessel vasculitis. The GC genotype of IL6 rs1800795 was suggested by the analyses to be related to low prevalence of vasculitis, especially for large and medium vessels.

Expression of Tumor-Related Macrophages and Cytokines After Surgery of Triple-Negative Breast Cancer Patients and its Implications

Background

Triple-negative breast cancer (TNBC) has negative expression of progesterone receptor (PR) and estrogen receptor (ER), and low expression of human epithelial growth factor receptor-2 (HER-2). This study aimed to investigate the expressional profile of cytokines in TNBC patients with significant expression of macrophages.

Material/Methods

Immunohistochemical (IHC) S-P staining method was used to detect the tumor-associated macrophages (TAMs) marker CD68 expression in 48 cases of TNBC samples. The correlation between CD68 expression and prognosis was analyzed. Expressions of key cytokines – interleukin-6 (IL-6), IL-10, IL-12, IL-1β, chemokine (C-C motif) ligand-5 (CCL-5), and macrophage inflammatory protein-2 (MIP-2) – were quantified by RT-PCR and enzyme-linked immunosorbent assay (ELISA).

Results

Thirty-four out of 48 TNBC samples (71.4%) had CD68-positive expression. IL-6 and CCL-5 were up-regulated in high-infiltrated tumors when compared to low-infiltrated samples. Other cytokines had no significant difference regarding the expression level across groups.

Conclusions

TAMs were up-regulated in most TNBC patients after the surgery. Its expression suggested unfavorable prognosis, especially in the high-infiltrated group. Those tumors with more macrophage also had elevated expression of cytokine IL-6 and chemotactic factor CCL-5, both of which have potency to be clinical index and drug target for TNBC.

Genetic association of IL-6, TNF-α and SDF-1 polymorphisms with serum cytokine levels in diabetic foot ulcer

The IL-6 -174G/C (rs1800795), TNF-α -308G/A (rs1800629) and -238G/A (rs361525) and SDF-1 801G/A (rs1801157) are well characterized SNPs which have previously been linked to various diabetic complications. However, the involvement of these SNPs in DFU remains poorly studied. In the present study we looked at the association of these SNPs with DFU (disease phenotype) and correlated it with the serum levels of cytokines (intermediate phenotype) along with other clinical risk factors of DFU (adiponectin, leptin and hsCRP). Genotyping was carried out in Normal glucose tolerance ((NGT)/Control=106), T2DM without DFU (T2DM=139), T2DM with neuropathy (DFU-DN=191) and T2DM with PVD (DFU-PVD=79) subjects by PCR-RFLP and the serum cytokine levels were determined by ELISA. IL-6 -176 "C" allele conferred significant protection against T2DM but not against DFU. TNF-α -308 "A" allele (but not -238 SNP) conferred significant susceptibility towards both T2DM and DFU-DN. The SDF-1 "A" allele conferred significant protection against both DM and DFU-DN but not against DFU-PVD. Further, these alleles were shown to influence the serum cytokine/chemokine levels under diabetic conditions. Thus SNPs in cytokine/chemokine genes serve as valuable biomarkers for DFU.

IL6 genotype, tumour ER-status, and treatment predicted disease-free survival in a prospective breast cancer cohort

Background

In breast cancer, high levels of the inflammatory cytokine interleukin-6 (IL-6) have been associated with disease-free survival and treatment resistance. Increased serum levels of IL-6 have been correlated with increased levels of NF-κβ and aromatase expression in adipose tissue. Several IL6 single nucleotide polymorphisms have been associated with breast cancer prognosis, but the impact may differ depending on tumour oestrogen receptor (ER) status. This translational study investigated the association between IL6 genotypes, ER-status, and treatment on the risk of early events among breast cancer patients.

Methods

The study included 634 25- to 99-year-old primary breast cancer patients in Sweden from 2002–2008. Genotyped IL6 single nucleotide polymorphisms rs1800797, rs1800796, rs1800795, and rs2069849 were analysed separately and as diplotypes. Disease-free survival was assessed for 567 patients. Clinical data, patient-, and tumour-characteristics were obtained from questionnaires, patient charts, population registries, and pathology reports.

Results

The median follow-up time was 5.1 years. IL6 diplotype was not associated with early events for all 567 patients, but AGCC/AGCC diplotype-carriers with ER-negative tumours had an increased risk, (adjusted Hazard Ratio (HR) = 5.91, 95% CI: 1.28–27.42). Any C-carriers (rs1800795) with ER-negative tumours had a higher risk of early events than GG-carriers with ER-negative tumours, (adjusted HR = 3.76, 95% CI: 1.05–13.43), particularly after radiotherapy (adjusted HR = 7.17, 95% CI: 1.16–32.28). Irrespective of ER-status, chemotherapy-treated Any C-carriers had a higher risk of early events than GG-carriers (adjusted HR = 3.42, 95% CI: 1.01–11.54).

Conclusions

The main finding of the present study was that IL6 genotype was strongly associated with early events among patients with ER-negative tumours, particularly among radiotherapy-treated patients, and among chemotherapy-treated patients irrespective of ER-status. The high risk for early events observed in these subgroups of patients suggests that combined information on IL6 genotype, tumour ER-status, and breast cancer treatment may represent a tool for identifying patients who require more personalised treatment.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2407-14-759) contains supplementary material, which is available to authorized users.

Relationship between Interleukin-6 gene polymorphism and hippocampal volume in antipsychotic-naïve schizophrenia: evidence for differential susceptibility?

Background

Various lines of evidence including epidemiological, genetic and foetal pathogenetic models suggest a compelling role for Interleukin-6 (IL-6) in the pathogenesis of schizophrenia. IL-6 mediated inflammatory response triggered by maternal infection or stress induces disruption of prenatal hippocampal development which might contribute towards psychopathology during adulthood. There is a substantial lack of knowledge on how genetic predisposition to elevated IL-6 expression effects hippocampal structure in schizophrenia patients. In this first-time study, we evaluated the relationship between functional polymorphism rs1800795 of IL-6 and hippocampal gray matter volume in antipsychotic-naïve schizophrenia patients in comparison with healthy controls.

Methodology

We examined antipsychotic-naïve schizophrenia patients [N = 28] in comparison with healthy controls [N = 37] group matched on age, sex and handedness. Using 3 Tesla – MRI, bilateral hippocampi were manually segmented by blinded raters with good inter-rater reliability using a valid method. Additionally, Voxel-based Morphometry (VBM) analysis was performed using hippocampal mask. The IL-6 level was measured in blood plasma using ELISA technique. SNP rs1800795 was genotyped using PCR and DNA sequencing. Psychotic symptoms were assessed using Scale for Assessment of Positive Symptoms and Scale for Assessment of Negative Symptoms.

Results

Schizophrenia patients had significantly deficient left and right hippocampal volumes after controlling for the potential confounding effects of age, sex and total brain volume. Plasma IL-6 levels were significantly higher in patients than controls. There was a significant diagnosis by rs1800795 genotype interaction involving both right and left hippocampal volumes. Interestingly, this effect was significant only in men but not in women.

Conclusion

Our first time observations suggest a significant relationship between IL-6 rs1800795 and reduced hippocampal volume in antipsychotic-naïve schizophrenia. Moreover, this relationship was antithetical in healthy controls and this effect was observed in men but not in women. Together, these observations support a “differential susceptibility” effect of rs1800795 in schizophrenia pathogenesis mediated through hippocampal volume deficit that is of possible neurodevelopmental origin.

Interleukin-6 -634C/G polymorphism is associated with lung cancer risk: a meta-analysis

Several studies have examined the associations of polymorphisms in interleukin-6 (IL6) with lung cancer (LC) risk. However, the results were conflicting. Thus, a meta-analysis was conducted to determine the relationship between IL6 polymorphisms and LC risk. Databases including PubMed, EMBASE, Wanfang, and China National Knowledge Infrastructure (CNKI) were searched. Data were extracted and pooled odds ratios (OR) with 95% confidence intervals (CI) were calculated. Thirteen studies were included in this meta-analysis. Overall, a significant association between IL6 -634C/G polymorphism and LC susceptibility was observed for GG + CG vs. CC (OR = 1.33, 95% CI 1.20-1.47, P < 0.00001). This polymorphism was also significantly associated with LC risk in Asians (OR = 1.33, 95% CI 1.20-1.47, P < 0.00001), female patients (OR = 1.30, 95% CI 1.11-1.52, P = 0.0009), male patients (OR = 1.25, 95% CI 1.03-1.52, P = 0.02), non-small cell lung cancer patients (OR = 1.21, 95% CI 1.03-1.41, P = 0.02), small cell lung cancer patients (OR = 1.91, 95% CI 1.23-2.97, P = 0.004), smokers (OR = 1.42, 95% CI 1.21-1.65, P < 0.0001), and non-smokers (OR = 1.32, 95% CI 1.13-1.53, P = 0.0003), respectively. No significant result was found for IL6 -174C/G polymorphism. This meta-analysis suggested that IL6 -634C/G polymorphism was a risk factor for LC.