Identification of haplotype tag single nucleotide polymorphisms within the nuclear factor-κB family genes and their clinical relevance in patients with major trauma

Abstract

Introduction: Nuclear factor-κB (NF-κB) family plays an important role in the development of sepsis in critically ill patients. Although several single nucleotide polymorphisms (SNPs) have been identified in the NF-κB family genes, only a few SNPs have been studied.

Methods: A total of 753 patients with major blunt trauma were included in this study. Tag SNPs (tSNPs) were selected from the NF-κB family genes (NFKB1, NFKB2, RELA, RELB and REL) through construction of haplotype blocks. The SNPs selected from genes within the canonical NF-κB pathway (including NFKB1, RELA and REL), which played a critical role in innate immune responses were genotyped using pyrosequencing method and analyzed in relation to the risk of development of sepsis and multiple organ dysfunction (MOD) syndrome. Moreover, the rs842647 polymorphism was analyzed in relation to tumor necrosis factor α (TNF-α) production by peripheral blood leukocytes in response to bacterial lipoprotein stimulation.

Results: Eight SNPs (rs28362491, rs3774932, rs4648068, rs7119750, rs4803789, rs12609547, rs1560725 and rs842647) were selected from the NF-κB family genes. All of them were shown to be high-frequency SNPs in this study cohort. Four SNPs (rs28362491, rs4648068, rs7119750 and rs842647) within the canonical NF-κB pathway were genotyped, and rs842647 was associated with sepsis morbidity rate and MOD scores. An association was also observed between the rs842647 A allele and lower TNF-α production.

Conclusions: rs842647 polymorphism might be used as relevant risk estimate for the development of sepsis and MOD syndrome in patients with major trauma.

Figures

Figure 1

Overview of selected haplotype tag single-nucleotide polymorphisms (htSNPs) within the entireNFKB2,RELA,RELBandRELgenes. Linkage disequilibrium (LD) plot of the SNPs with a minor allele frequency (MAF) ≥5% within the (A)NFKB2, (B)RELA, (C)RELB and (D)REL genes and 5-kb up- and downstream regions is displayed using an r2 black and white color scheme. Black represents very high LD (r2 = 1), and white indicates the absence of correlation (r2 = 0) between SNPs. The three SNPs within the entire NFKB2 gene did not have a strong correlation between each other or with others. The htSNPs and SNPs that are indirectly measured by them are listed with corresponding r2 values. Major and minor alleles of the selected tag SNPs are given with their frequencies, on the basis of the HapMap data for Chinese individuals from Beijing.

Figure 2

Effect of the rs842647 polymorphism on lipolysaccharide (LPS)-induced TNF-α production. The whole-blood samples collected from trauma patients (n = 30 for the GG and GA genotype, n = 15 for the AA genotype) immediately after admission were mixed at a 1:1 ratio (vol/vol) with RPMI 1640 culture medium and incubated with 100 ng/mL bacterial LPS at 37°C for 4 hours. TNF-α production was determined by a sandwich ELISA. The data are presented as mean ± SD. One-way analysis of variance was used to assess statistical significance. *P = 0.027 for recessive association (AA versus GG + GA).