Role of IL-6, IL-10 and TNFα Gene Variants in Preterm Birth

Background: The association of gene variants for interleukin 6 (IL-6) (rs1800796), interleukin 10 (IL-10) (rs1800896) and tumor necrosis factorα (TNFα (rs1800629) with the occurrence of spontaneous preterm birth (PTB) was investigated to determine whether these genetic variants are a risk factor. Methods: A total of 199 blood samples from pregnant women who had given birth prematurely and 200 control blood samples were analyzed to determine single nucleotide polymorphisms (SNPs) of genes for IL-6 (rs1800796), IL-10 (rs1800896) and TNFα (rs1800629). The control samples were samples from pregnant women with term delivery. The isolation of DNA was performed on mini-spin columns according to the manufacturer's protocol. The quality and purity of the isolated DNA were tested using a Qubit 3 fluorometer. Genotyping was performed with an ABI PRISM 7500 SDS using TaqMan SNP genotyping assays. The genotypes obtained were analyzed using the 7500 Software v2.3 package. Results: Carriers of the A/A genotype for the rs1800629 SNP of the TNFα gene have a 4.81 times greater chance of late-onset PTB compared to carriers of the G/G and A/G genotypes in the recessive inheritance model. The presence of the G/G genotype in the recessive inheritance model compared with the G/A and A/A genotypes for the rs1800896 SNP of the IL-10 gene represents a potentially protective factor, with mothers in the term-birth group having an almost 2-fold lower odds of PTB in general and an almost 10-fold lower odds of early PTB. On the other hand, carriers of the A/G genotype of rs1800896 have a 1.54-fold higher chance of preterm birth in general and a 1.6-fold higher chance of late preterm birth in the superdominant inheritance model compared to the A/A and G/G genotypes in the group of mothers with PTB. In this study, no association was found between PTB and the rs1800796 SNP of the IL-6 gene. Conclusions: rs1800629 in mothers was associated with PTB. rs1800896 shows a potentially protective effect for the occurrence of PTB in this study. No association was found between PTB and rs1800796.

A review of key cytokines based on gene polymorphism in the pathogenesis of pre-eclampsia

Although a number of theories have been suggested, including roles for oxidative stress, an abnormal maternal-fetal interface, and genetic and environmental factors, the etiopathology of pre-eclampsia (PE) remains unclear. Maternal immune tolerance is important for maintaining pregnancy, and researchers have increasingly focused on the critical roles of cytokines in the pathogenesis of PE in recent years. The assessment of candidate genetic polymorphisms in PE could partially elucidate the mechanisms of susceptibility to disease, and contribute to seeking for new diagnosis and treatment methods of PE. PE can lead to severe complications, and even the death of both mother and fetus. Although the complex pathology is not yet clear, some evidence suggested that the occurrence of PE is related to inflammatory factors. We reviewed the current understandings of roles of cytokines in PE, and provided an extensive overview of the role of single nucleotide chain polymorphisms (SNPs) in the genes potentially underlying the pathophysiology of PE.

Are genetic variations in IL-1β and IL-6 cytokines associated with the risk of pre-eclampsia? Evidence from a systematic review and meta-analysis

OBJECTIVE

This systematic review and meta-analysis study was performed to assess the potential association between interleukin-1 beta (IL-1β) single nucleotide polymorphisms (SNPs) (rs1143634 and rs16944) and interleukin-6 (IL-6) SNP (rs1800795) and pre-eclampsia (PE).

METHODS

A comprehensive literature search was conducted in the international search engines and databases, including MEDLINE (via PubMed), Scopus, and Web of Science (ISI) up to 9 March 2021. After retrieving relevant articles, data extraction was performed by four authors independently. Pooled ORs and corresponding 95% CIs were used to evaluate the association between IL-1β and IL-6 polymorphisms and PE risk. Cochran's Q test was used to check heterogeneity, and the I² index was calculated for measuring the heterogeneity between the estimations of included studies.

RESULTS

After reviewing fully published studies, 21 studies were included in this study based on the eligibility criteria. Our results showed that rs16944 and rs1143634 of IL-1β were significantly associated with the risk of PE. Regarding rs16944, the minor C allele significantly decreased the risk of PE (C vs. T: OR = 0.79, 95% CI = 0.69-0.90). In contrast, the minor T allele of rs1143634 significantly increased the risk of PE (T vs. C: OR = 1. 28, 95% CI = 1.04-1.58). There was no significant association between IL-6 rs1800795 (C vs. G: OR = 1.04, 95% CI = 0.93-1.16) polymorphism and PE risk.

CONCLUSIONS

In conclusion, this meta-analysis suggests rs1143634 and rs16944 polymorphisms of IL-1β are related to the risk of PE.

The determinant role of IL-6 in the establishment of inflammation leading to spontaneous preterm birth

Preterm birth (PTB) and its consequences are a major public health concern as preterm delivery is the main cause of mortality and morbidity at birth. There are many causes of PTB, but inflammation is undeniably associated with the process of premature childbirth and fetal injury. At present, treatments clinically available mostly involve attempt to arrest contractions (tocolytics) but do not directly address upstream maternal inflammation on development of the fetus. One of the possible solutions may lie in the modulation of inflammatory mediators. Of the many pro-inflammatory cytokines involved in the induction of PTB, IL-6 stands out for its pleiotropic effects and its involvement in both acute and chronic inflammation. Here, we provide a detailed review of the effects of IL-6 on the timing of childbirth, its occurrence during PTB and its indissociable roles with associated fetal tissue damage.

Association of IL-6 -176G > C Polymorphism with Susceptibility to Preeclampsia: A Systematic Review and Meta-Analysis

Background: Many studies have described the influence of -176G > C polymorphism of the IL-6 gene on susceptibility to preeclampsia. However, the results have remained inconclusive and controversial. Therefore, we performed a meta-analysis to more precisely determine the association between the IL-6 -176G > C polymorphism and preeclampsia risk. Methods: Electronic databases including PubMed, Embase, Web of Science, and CNKI were searched up to August 15, 2019. The pooled odds ratios (ORs) and their corresponding 95% confidence intervals (CIs) were used to calculate the association. Results: A total of 12 studies with 1,821 preeclampsia cases and 3,339 controls were selected. Overall, no significant association was found between IL-6 -176G > C polymorphism and preeclampsia risk. In the stratified analyses by ethnicity, there was a significant association in Asians, but not in Caucasians and mixed populations. Conclusions: The results of meta-analysis indicated that IL-6 -176G > C polymorphism was not significantly associated with risk of preeclampsia in overall population.

IL-6: An endogenous activator of MMP-9 in preterm birth

Preterm birth or PTB (<37 weeks) is a heterogeneous phenotype with numerous biological pathways. The lack of explanation due to complex pathways, inconsistent observations indicates the need for employing the role of genetic determinants to anticipate the danger of PTB. In this present study, we investigated the possible gene-gene interaction of five SNPs with PTB and its association with total MMP-9 levels. A total of 510 recruitments (250 terms and preterm each) were made and were genotyped by Restriction Fragment length polymorphism (RFLP). Generalized Multifactor Dimensionality Reduction (GMDR) method was carried out for determining gene-gene interaction. ANOVA and t-test were used to identify the association of IL-6 polymorphism with PTB alone and correspondingly with PTB and low birth weight infants (i.e. < 2500 kg). The combination of IL-6 and MMP-9 and MMP-1, MMP-8 and MMP-9 polymorphism was selected through GMDR analysis concerning mothers with preterm and term birth (accuracy 0.5921 and 0.8030 with Cross-Validation Consistency (CVC) 10/10 respectively). Increased expression of MMP-9 was reported in cases in those mothers carrying IL-6 G allele, which was profoundly associated with PTB independently. IL-6 polymorphisms showed synergistic effects in terms of increased total MMP-9 levels in the present study.

Associations between tumor necrosis factor-α and interleukin-6 polymorphisms and unexplained recurrent spontaneous abortion risk: A meta-analysis

To evaluate the associations between Tumor necrosis factor-α (TNF-α)(-238G>A) and Interleukin-6 (IL-6)(-174G>C) polymorphism and risk of unexplained recurrent spontaneous abortion (URSA).Correlated case-control studies were collected by computer retrieval. A meta-analysis was conducted by Stata 12.0 software to analysis the strength of association between polymorphism of TNF-α -238G>A and IL-6 -174G>C and URSA.Twenty-one articles with twenty-two studies were included, of which 12 and 10 studies were respectively related to mutation of TNF-α -238G>A, IL-6 -174G>C and URSA. The integrated results showed that the TNF-α-238G>A gene mutation was significantly correlated with the risk of URSA under homozygote model (AA vs GG;OR 1.533,95% CI 1.022-2.301) and recessive model (AA vs GG+AG;OR 1.571,95%CI 1.050-2.350)(P < .05). There was no association between URSA and TNF-α -238G>A under heterozygote model (AG vs GG;OR 0.963,95% CI 0.816-1.137), dominant model (AA+AG vs GG; OR 1.031,95%CI 0.880-1.209) and additive model (A vs G;OR 1.046,95%CI 0.909-1.203)(P > .05). The results of subgroup analysis based on ethnicity showed that -238G>A was significantly correlated with the risk of URSA in Asians under all gene models except for heterozygote model (AG vs GG; OR 1.129,95% CI 0.857-1.487) (P < .05). In Caucasians, it was dominant model (AA+AG vs GG; OR 1.430,95%CI 1.040-1.965) (P < .05) rather than others that showed relationship with URSA. From the integrated results, association was manifested between -174G>C and URSA under all gene models (P < .05) except for recessive model (CC vs GG+CG, OR 1.166, 95%CI 0.938-1.449) (P > .05), which is identical to subgroup analysis based on ethnicity.It is of great guiding significance for screening out and preventing URSA among high-risk women to test on TNF-α -238G>A and IL-6 -174G>C under gene models mentioned above which are highly associated with the risk of URSA, which can act as biological markers for URSA.

Effect of maternal and neonatal interleukin-6 - 174 G/C polymorphism on preterm birth and neonatal morbidity

OBJECTIVE

The aim of this study was to analyze maternal and neonatal interleukin 6 (IL-6) (-174 G/C) polymorphism and to determine effect on preterm birth and neonatal morbidity.

STUDY DESIGN

One hundred and sixty-four mothers (100 term births, 64 preterm births) and 183 newborn infants who were 100 healthy term and 83 preterm babies followed in newborn intensive care units were evaluated. PCR-RFLP was performed for IL-6 (-174 G/C) genotyping.

RESULTS

The rate of GG genotype in mothers of term and preterm infants were 54% (n = 54/100), 75% (n = 48/64), respectively (p > .05) and the rate of GC + CC genotype was 46% (n = 46/100) and 25% (n = 16/64) in mothers giving term and preterm birth (PTB), respectively (p < .05). Additionally, the rate of GG genotype was 65% (n = 65/100) and 81.9% (n = 68/83) in term infants and preterm infants, respectively. GC + CC genotype was 35% (n = 35/100) in term infants and 18.1% (n = 15/83) in preterm infants (p < .05). The effect of IL-6 (-174) GC + CC genotype on PTB was statistically significant.

CONCLUSION

The IL-6 174 G/C gene polymorphism was significantly different between mothers who were giving to term and preterm birth. The presence of polymorphism is protective against preterm birth and was not associated with neonatal outcome.

Spontaneous preterm birth and single nucleotide gene polymorphisms: a recent update

Background

Preterm birth (PTB), birth at <37 weeks of gestation, is a significant global public health problem. World-wide, about 15 million babies are born preterm each year resulting in more than a million deaths of children. Preterm neonates are more prone to problems and need intensive care hospitalization. Health issues may persist through early adulthood and even be carried on to the next generation. Majority (70 %) of PTBs are spontaneous with about a half without any apparent cause and the other half associated with a number of risk factors. Genetic factors are one of the significant risks for PTB. The focus of this review is on single nucleotide gene polymorphisms (SNPs) that are reported to be associated with PTB.

Results

A comprehensive evaluation of studies on SNPs known to confer potential risk of PTB was done by performing a targeted PubMed search for the years 2007–2015 and systematically reviewing all relevant studies. Evaluation of 92 studies identified 119 candidate genes with SNPs that had potential association with PTB. The genes were associated with functions of a wide spectrum of tissue and cell types such as endocrine, tissue remodeling, vascular, metabolic, and immune and inflammatory systems.

Conclusions

A number of potential functional candidate gene variants have been reported that predispose women for PTB. Understanding the complex genomic landscape of PTB needs high-throughput genome sequencing methods such as whole-exome sequencing and whole-genome sequencing approaches that will significantly enhance the understanding of PTB. Identification of high risk women, avoidance of possible risk factors, and provision of personalized health care are important to manage PTB.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-016-3089-0) contains supplementary material, which is available to authorized users.

Polymorphisms in Inflammatory Mediator Genes and Risk of Preeclampsia in Taiyuan, China

Excessive maternal inflammatory response is involved in the pathogenesis of preeclampsia. Few epidemiologic studies have investigated the associations between genetic variations in the inflammatory mediator genes and preeclampsia risk, and these studies have reached inconsistent results. We examined 31 single-nucleotide polymorphisms in IL-1A, IL-1B, IL-1R1, IL-2RA, IL-5RA, IL-6, IL-6R, TNFSF11, TNFRSF11A, IL-28RA, IRAK4, and KIT genes and the risk of preeclampsia and its clinical subtypes in a nested case-control study including 203 preeclampsia cases and 233 controls. We found that IL-1R1, IL-5RA, IL-6R, and TNFSF11 were associated with the risk of preeclampsia. Although the significant associations observed for preeclampsia overall were mainly seen for late-onset preeclampsia and severe preeclampsia, IL-6R (rs2229238) and TNFSF11 (rs9525643) polymorphisms were associated with the risk of early-onset preeclampsia. TNFSF11 (rs2200287 and rs2148072) polymorphisms were associated with risk of mild preeclampsia. Our study provided the first evidence that genetic variations in inflammatory mediator genes IL-1R1, IL-6R, TNFSF11, and IL-5RA were associated with preeclampsia risk, and the risk varied by preeclampsia subtypes.

Severe preeclampsia: association of genes polymorphisms and maternal cytokines production in Brazilian population

INTRODUCTION

Preeclampsia (PE) is a multi-system disorder of pregnancy characterized by hypertension and proteinuria. Healthy pregnancy is associated with a controlled inflammatory process, which is exacerbated in PE in response to excessive placental stimuli. Gene expression levels can affect inflammation and immune regulation. It is known that differences in cytokine allele frequencies amongst populations may contribute to difference in the incidence of several diseases.

OBJECTIVE

The aim of this study was to investigate the frequency of TNF-α, IL-6, IFN-γ and IL-10 genes polymorphisms and their relationship with the cytokines plasma levels in PE.

METHODS

A total of 281 women were included in this study; 116 with severe PE, 107 normotensive pregnant and 58 non-pregnant women. Cytokine genotyping was carried out by the polymerase chain reaction. The analyzed polymorphisms were: TNF-α (-308 G→A), IL-10 (-1082 G→A), IL-6 (-174 G→C), and IFN-γ (+874 A→T). Cytokine plasma levels were measured by Cytometric Bead Array method.

RESULTS

A higher frequency of the IFN-γ (+874) T/T genotype in severe PE comparing to normotensive pregnant women was found (P<0.001). TNF-α, IL-6 and IFN-γ plasma levels were higher in PE women compared to non-pregnant women (P<0.001; P<0.001; P=0.004). IL-6 and IFN-γ levels were also higher in PE women compared to normotensive pregnant (P<0.001; P=0.010). IL-10 levels were higher in normotensive pregnant women compared to PE (P<0.001). IFN-γ and IL-6 genes polymorphisms influenced the genic expression in PE and normotensive pregnant women, respectively.

CONCLUSIONS

These results suggest that IFN-γ seems to play a role in PE occurrence.

Polymorphisms in inflammatory genes are associated with term small for gestational age and preeclampsia

PROBLEM

Inflammatory biomarkers are associated with preeclampsia (PE) and poor fetal growth; however, genetic epidemiologic studies have been limited by reduced gene coverage and the exclusion of African American mothers.

METHOD OF STUDY

Cases and controls (N = 1646) from a pregnancy cohort were genotyped for 503 tagSNPs in 40 genes related to inflammation. Gene-set analyses were stratified by race and were followed by a single SNP analysis within significant gene sets.

RESULTS

Gene-level associations were found for IL6 and KLRD1 for term small for gestational age (SGA) among African Americans. LTA/TNF and TBX21 were associated with PE among European Americans. The strongest association was for PE among European Americans for an upstream regulator of TNF with RR = 1.8 (95% CI 1.1-2.7).

CONCLUSION

Although previous studies have suggested null associations, increased tagging and stratification by genetic ancestry suggests important associations between IL6 and term SGA for African Americans, and a TNF regulator and PE among European Americans (N = 149).

Effect of interleukin-6 polymorphism on risk of preterm birth within population strata: a meta-analysis

Background

Because of the role of inflammation in preterm birth (PTB), polymorphisms in and near the interleukin-6 gene (IL6) have been association study targets. Several previous studies have assessed the association between PTB and a single nucleotide polymorphism (SNP), rs1800795, located in the IL6 gene promoter region. Their results have been inconsistent and SNP frequencies have varied strikingly among different populations. We therefore conducted a meta-analysis with subgroup analysis by population strata to: (1) reduce the confounding effect of population structure, (2) increase sample size and statistical power, and (3) elucidate the association between rs1800975 and PTB.

Results

We reviewed all published papers for PTB phenotype and SNP rs1800795 genotype. Maternal genotype and fetal genotype were analyzed separately and the analyses were stratified by population. The PTB phenotype was defined as gestational age (GA) < 37 weeks, but results from earlier GA were selected when available. All studies were compared by genotype (CC versus CG+GG), based on functional studies.

For the maternal genotype analysis, 1,165 PTBs and 3,830 term controls were evaluated. Populations were stratified into women of European descent (for whom the most data were available) and women of heterogeneous origin or admixed populations. All ancestry was self-reported. Women of European descent had a summary odds ratio (OR) of 0.68, (95% confidence interval (CI) 0.51 – 0.91), indicating that the CC genotype is protective against PTB. The result for non-European women was not statistically significant (OR 1.01, 95% CI 0.59 - 1.75). For the fetal genotype analysis, four studies were included; there was no significant association with PTB (OR 0.98, 95% CI 0.72 - 1.33). Sensitivity analysis showed that preterm premature rupture of membrane (PPROM) may be a confounding factor contributing to phenotype heterogeneity.

Conclusions

IL6 SNP rs1800795 genotype CC is protective against PTB in women of European descent. It is not significant in other heterogeneous or admixed populations, or in fetal genotype analysis.

Population structure is an important confounding factor that should be controlled for in studies of PTB.

Profile of inflammatory mediators in gestational diabetes mellitus: phenotype and genotype

PROBLEM

Our study aimed to assess in vitro production of IL-10, IL-6, TNF-A, and adiponectin serum levels in pregnant women with and without gestational diabetes mellitus (GDM) and to investigate a possible association between GDM and IL-10-1082 A>G (rs1800896), IL-6-174 G>C (rs1800795), TNF-A-308 G>A (rs1800629), adiponectin +45 T>G (rs2241766), and adiponectin-11377 C>G (rs266729) gene polymorphisms.

METHOD OF STUDY

This case-control study included 79 women with GDM and 169 healthy controls (C) grouped according to pre-pregnancy BMI. IL-10, IL-6, and TNF-A culture supernatant and adiponectin serum levels were assessed by ELISA. DNA genotype was performed by PCR-RFLP.

RESULTS

Adiponectin levels were significantly higher in C than GDM women, even within the same BMI category. Cytokines levels were similar between the groups. There were no associations between GDM and the analyzed gene polymorphisms.

CONCLUSIONS

Women with GDM have significantly lower adiponectin levels in the third trimester, regardless of BMI.

IL-1β, IL-6 promoter, TNF-α promoter and IL-1RA gene polymorphisms and the risk of preterm delivery due to preterm premature rupture of membranes in a population of Polish women

INTRODUCTION

Our previous study revealed that anti-inflammatory cytokine gene polymorphisms increase the risk of spontaneous preterm delivery (PD) in a population of Polish women. Different genetic background of PD due to preterm premature rupture of membranes (pPROM) than PD without pPROM has been suggested. The aim of this study was to examine the relationship between the maternal carriage of polymorphic alleles of the following genes: interleukin 1β(IL-1β [+3953C>T]), interleukin 6 promoter (IL-6 [-174G>C]), tumour necrosis factor promoter (TNF-α [-308G>A]) and interleukin 1 receptor antagonist (IL-1RN) and the risk of PD caused exclusively by pPROM in a population of Polish women.

MATERIAL AND METHODS

A case-control study. 95 Caucasian women were examined including 32 cases and 63 controls. Case subjects experienced a delivery at less than 36 weeks and 6 days of gestation due exclusively to pPROM while control subjects gave birth at term. Polymorphisms were determined by polymerase chain reaction-restriction fragment length polymorphism analysis (PCR-RFLP).

RESULTS

NO STATISTICALLY SIGNIFICANT RELATIONSHIP BETWEEN POLYMORPHISMS OF EXAMINED GENES AND RISK OF PD DUE TO PPROM IN A POPULATION OF POLISH WOMEN WAS FOUND: OR = 0.84 (95% CI: 0.34-2.01) for IL-1β, OR = 0.77 (95% CI: 0.27-2.13) for IL-6, OR = 0.72 (95% CI: 0.26-1.90) for TNF-α and OR = 1.74 (95% CI: 0.66-4.64) for IL-1RN.

CONCLUSIONS

Maternal carriage of polymorphic alleles of IL-1β, IL-6 promoter, TNF-α promoter and IL-1RA seems to have no impact on the risk of PD due to pPROM in the population of Polish women.The genetic contribution and pathomechanism of PD related to pPROM seems to differ from those of spontaneous PD without pPROM.

Umbilical cord serum cytokine levels and risks of small-for-gestational-age and preterm birth

While elevated levels of proinflammatory cytokines are clearly associated with preterm birth, the relation between cytokines and fetal growth is unclear. The authors examined associations between umbilical cord serum cytokine concentrations and risk of small-for-gestational-age (SGA) and preterm birth. This cross-sectional analysis was nested within a National Institute of Child Health and Human Development-University of Alabama population-based cohort study of high-risk prenatal care patients in Jefferson County, Alabama. Patients were enrolled between 1985 and 1988. For 370 singletons, umbilical cord serum concentrations of interferon gamma (IFN-gamma), tumor necrosis factor alpha, and interleukins 12p70, 4, and 10 were determined. Associations between each cytokine and SGA and preterm delivery were evaluated using log binomial regression. Increasing log concentration of tumor necrosis factor alpha was associated with an increased risk of preterm birth (risk ratio (RR) = 2.00, 95% confidence interval (CI): 1.31, 3.06). IFN-gamma was associated with a decreased risk of SGA birth (RR = 0.78, 95% CI: 0.61, 1.01). After stratification for preterm birth status, the association between IFN-gamma concentration and SGA birth was pronounced among preterm babies (RR = 0.56, 95% CI: 0.31, 1.01). The observations regarding IFN-gamma, which is involved in the activation of adaptive immune responses and regulation of trophoblast function, suggest that IFN-gamma levels at birth may be related to fetal growth restriction.

Contribution of interferon-gamma receptor 1 gene polymorphisms to pre-eclampsia in China

PROBLEM

As gene polymorphisms of cytokines receptors have been found to significantly influence cell responses to cytokines, the aim of this study was to test the hypothesis that IFN-gamma receptor 1 (IFNGR1) gene polymorphisms may contribute to the pathogenesis of pre-eclampsia.

METHOD OF STUDY

One hundred and sixty-four pre-eclamptic patients (121 patients with mild pre-eclampsia and 43 patients with severe pre-eclampsia) and 171 controls were included. Polymorphisms of the IFNGR1 gene at positions -611, -270, +56 and +95 were genotyped with the matrix-assisted laser desorption/ionization time of flight mass spectrometry.

RESULTS

This study showed a positive association between -56C/C genotype (OR = 1.7; 95% CI = 1.1-2.7) and pre-eclampsia. Although the genotype frequencies (except for -56C/C) of the two polymorphisms were comparable between cases and controls, higher frequency of the -611A/-56C haplotype (OR = 1.450; 95% CI = 1.070-1.966) was noticed in patients versus controls. All patients and controls were homozygous for the -270T/T and +95T/T genotypes. Specifically, the frequency of the -56C allele (OR = 1.838; 95% CI = 1.127-2.995) was higher among patients with severe pre-eclampsia.

CONCLUSION

The IFNGR1 gene polymorphisms may contribute to the pathogenesis of pre-eclampsia in our population.