Comparison of methods for determination of interleukin 6 G(-174)C promoter polymorphism

Maternal interleukin-6 (-174) C/C polymorphism is associated with chorioamnionitis and cystic periventricular leucomalacia of the preterm infant

OBJECTIVE

To evaluate the association between maternal interleukin (IL)-6 G(-174)C polymorphism and cystic periventricular leukomalacia (cPVL) of the preterm newborn.

STUDY DESIGN

After searching a local database, we recruited 132 preterm infants with diagnosis of cPVL, 44 Caucasian mothers were also recruited to participate in this candidate gene-association study at a single teritary care center. Data related to maternal IL-6 G(-174)C polymorphisms were compared with 41 controls, and furthermore compared with data from umbilical cord blood samples from a consecutive birth cohort of 395 healthy newborns, and published data from Caucasian populations including 1104 adults, respectively. In addition, subgroup analysis was performed in cases with either history of preterm premature rupture of the membranes (PPROM) or clinical chorioamnionitis (CCA). IL-6 genotyping was performed using an allele-specific polymerase chain reaction technique.

RESULT

Frequencies of the IL-6 G(-174)C polymorphisms did not differ between cases (GG, 29.5%; GC, 54.5% and CC, 15.9%) and controls (GG, 34.2; GC, 51.2 and CC, 14.6%). Subgroup analysis of 31 cases with history of PPROM (GG, 25.8; GC, 54.8 and CC 19.4%) and controls did not reveal significant differences, but a significantly higher frequency of the CC genotype was found in 23 cases with a history of CCA (34.8%) compared with controls by either univariate (P=0.032; odds ratio 3.11, 95% confidence interval (CI) 1.11 to 8.68) or multivariate analysis (P=0.049, odds ratio 2.54, 95% CI 1.01 to 6.45). These data were confirmed by a comparing the CC genotype frequency to 395 term controls (CC 14.7%, P=0.005) and to the mean CC genotype frequency of 1104 Caucasian adults (CC 15.6%, P<0.0001).

CONCLUSION

Frequencies of the IL-6 G(-174)C polymorphisms did not differ between groups. Subgroup analysis revealed an association of the CC genotype with CCA and cPVL in the preterm newborn.

The C-reactive protein (+)1444C/T alteration modulates the inflammation and coagulation response in human endotoxemia

BACKGROUND

C-reactive protein (CRP) plays a major role in the immune system and is an independent risk marker of cardiovascular disease. However, CRP's role in atherogenesis as innocent bystander, causative, or even protective agent, remains unresolved. The (+)1444C/T alteration in the CRP gene has been reported to determine basal CRP concentrations. We hypothesized that this alteration may also be associated with the degree of inflammatory response and coagulation activation in a well-standardized model of systemic inflammation.

METHODS

We administered 2 ng/kg endotoxin [Escherichia coli bacterial lipopolysaccharide (LPS)] intravenously to stimulate inflammation in 91 healthy young Caucasian male paid volunteers (age range, 19-40 years). Participants were confined to bed rest and fasted for 8.5 h after LPS infusion. We collected blood samples before LPS infusion and at 0, 2, 6, and 24 h after LPS infusion to measure inflammation markers [interleukin 6 (IL6), tumor necrosis factor-alpha (TNFalpha)], temperature, and coagulation markers (prothrombin fragment F(1+2), D-dimer). We analyzed the CRP 3' untranslated variant with a mutagenic separated PCR assay.

RESULTS

Basal concentrations of high-sensitivity CRP were approximately 40% lower in (+)1444CC alteration carriers than in T homozygous (TT) allele carriers (P = 0.04). In contrast, basal IL6 concentrations were 2-fold higher in wild-type C homozygous (CC) than in TT individuals (P = 0.01). In response to the LPS challenge, CC individuals had 4-fold higher peak TNFalpha concentrations (P <0.01), >2.5-fold higher peak IL6 concentrations (P <0.01), and increased temperature (P <0.01). Twenty-four hours after LPS challenge, prothrombin fragment F(1+2) concentrations were 75% higher and D-dimer concentrations 50% higher in CC than in TT individuals (P <0.05).

CONCLUSIONS

Genetic factors regulating CRP concentrations also modulate the individual response to endotoxin-stimulated inflammation.

IL-10, IL-6 and CD14 polymorphisms and sepsis outcome in ventilated very low birth weight infants

BACKGROUND

Genetic variation in the innate immune system of the host may play a role in determining the risk of developing infection, as well as outcome from infection.

METHODS

Infectious complications were retrospectively determined in 293 (233 African-American (AA), 57 Caucasian and 3 Hispanic) mechanically ventilated very low birth weight (VLBW) infants (<1500 grams at birth) who were genotyped for the IL-6 -174 G/C, IL-10 -1082 G/A and CD14 -260 C/T single nucleotide polymorphisms (SNPs).

RESULTS

The IL-6 -174C allele was associated with an increased incidence of late blood stream infection (BSI) in AA but not Caucasian infants. In AA infants with the C allele the incidence of late BSI was 20/29 (69%) compared to 94/204 (46%) in homozygous GG infants (RR 2.6, 95% CI: 1.1-6.0, p = 0.021). The IL-10 -1082A allele was associated with an increased incidence of late BSI. One or more episodes of late BSI developed in 14 (35%) of 40 infants with the GG genotype, 71 (49%) of 145 infants with the GA genotype and 63 (58%) of 108 infants with the AA genotype (p = 0.036). Infants with the A allele (AA or GA genotypes) had an incidence of late BSI that was 134/253 (53%) compared to 14/40 (35%) in homozygous GG infants (RR 2.1, 95% CI: 1.04-4.19, p = 0.035). The CD14 -260 C/T SNP did not alter the overall risk for BSI in ventilated VLBW infants. Multiple BSI episodes were more common in the TT genotype group (CC: 17%, CT: 11%, TT: 30%, p = 0.022). This effect was due to the strong effect of the TT genotype on the incidence of multiple BSI in AA infants (CC: 15%, CT: 11%, TT: 39%, p = 0.003).

CONCLUSION

The IL-6 -174 G/C, IL-10 -1082 G/A and CD14 -260 C/T SNPs may alter risk for BSI in ventilated VLBW infants.

The (-174) G/C polymorphism in the interleukin-6 gene is associated with the severity of acute cerebrovascular events

BACKGROUND AND PURPOSE

Elevated plasma levels of interleukin-6 (IL-6) are associated with an increased risk and worse outcome of acute vascular events. A common G/C promoter polymorphism at nt (-174) of the IL-6 gene has been shown to affect basal IL-6 levels. Consequently, the IL-6 genotype may be associated with risk and outcome of ischemic stroke (IS). We investigated the statistical association between this polymorphism and cerebrovascular events, as well as the clinical outcome in patients with symptoms before the age of 60.

METHODS

We examined 214 patients of 60 years or less with acute ischemic stroke or transient ischemic attack (TIA) and 214 age- and sex-matched healthy control subjects for the (-174) IL-6 G/C polymorphism by mutagenic separated polymerase chain reaction (MS PCR). Clinical severity of the vascular event was evaluated by validated scales at predefined points of time.

RESULTS

In the total group of patients, the genotype and allele frequencies in the patient group (38% GG, 45% GC, 17% CC; allelic frequency: 60% G, 40% C) did not differ significantly from the control group. However, individuals homozygous for the (-174)G variant had significantly worse scores on the NIH Stroke Scale (NIHSS) already on admission and 1 week after the event. Also, patients with severe disability 1 week and 3 months after the event (Rankin Scale (RS) 4 or 5; NIH Stroke Scale> or =6) were significantly more often carriers of the GG genotype. In a multivariate analysis, the IL-6 (-174)GG genotype was significantly associated with severe disability after 1 week (RS 4-5; odds ratio (OR)=3.2, 95% CI: 1.5-6.6; p=0.002; NIHSS> or =6; OR=4.2, 95% CI: 1.6-11.1).

CONCLUSIONS

The (-174)GG-genotype of the IL-6 gene is associated with severe stroke in young patients with acute cerebrovascular events. Further studies with larger patient groups are warranted to confirm these findings.

Searching for cancer-associated gene polymorphisms: promises and obstacles

Low-penetrance genetic variations appear to form the most essential component of the heritability of cancer risk. Search for relevant polymorphic candidates faces significant obstacles, due to both the high number of potentially promising single nucleotide polymorphisms (SNPs) and the intrinsic difficulties in identification of weak gene-disease interactions. At present, extensive case-control studies can be applied only to a limited number of gene polymorphisms. Therefore, the choice of SNPs that deserve an exhaustive populational analysis is of primary importance. Preferences are usually given to those genetic pathways, whose variability and role in cancer causation have been already shown by prior studies. The available electronic databases and software tools may allow further SNP sorting, based on functional predictions. The design for the pilot study may need to be different from the one for large-scale case-control analysis. Some investigations justify non-random patient selection for preliminary assessment of low-penetrance effects, with the emphasis on particularly susceptible individuals (familial, early onset, multiple cancer cases). Other presumably accelerating approaches suggest a decisive exclusion of SNP candidates showing only marginal effects, relaxed formats for rapid dissemination of preliminary data, use of more demonstrative controls such as elderly tumor-free subjects, etc. These short-cuts cannot be properly validated for the time being, due to the paucity of identified low-penetrance risk modifiers. It is expected that the increasing capacities of available DNA collections, coupled with the rapid development of high-throughput genotyping technologies, will vastly accelerate the research on polygenic cancer susceptibility.

The Interleukin-6 G(−174)C Promoter Polymorphism Does Not Determine Plasma Interleukin-6 Concentrations in Experimental Endotoxemia in Humans

Background: Interleukin 6 (IL-6) is a pleiotropic cytokine that plays an essential role in the pathogenesis of acute and chronic infections. As the role of the IL-6 G(−174)C polymorphism in determining serum concentrations of IL-6 is controversial, we studied the genotype-specific IL-6 response in a well-standardized model of systemic inflammation.

Methods: A total of 76 healthy young males (age range, 19–35 years) received a single bolus of 2 ng/kg endotoxin [lipopolysaccharide (LPS)] intravenously. Plasma IL-6 was measured by enzyme immunoassay at 0, 2, 6, and 24 h after LPS infusion, and the IL-6 promoter genotype was analyzed by a mutagenic separated PCR assay.

Results: IL-6 increased 300-fold 2 h after LPS challenge and returned almost to normal within 24 h. Neither basal IL-6 nor the IL-6 response to LPS was significantly affected by the IL-6 promoter genotype.

Conclusions: The IL-6 G(−174)C promoter polymorphism does not significantly influence basal concentrations of IL-6 or peak IL-6 in human endotoxemia.