Cytokine gene polymorphisms influence mucosal cytokine expression, gastric inflammation, and host specific colonisation during Helicobacter pylori infection

Abstract

Background and aims: Recent studies linked cytokine gene polymorphisms to H pylori related gastric cancer development. The current study evaluated the role of cytokine gene polymorphisms for mucosal cytokine expression, the gastric inflammatory response, and bacterial colonisation during H pylori infection.

Patients and methods: In 207 H pylori infected patients with chronic gastritis, polymorphisms at different loci of the interleukin (IL)-10, IL-1B, IL-1 receptor antagonist (IL-1RN), tumour necrosis factor (TNF)-A, and interferon (IFN)-G genes were genotyped by polymerase chain reaction (PCR), restriction fragment length polymorphism (RFLP) analysis, and allelic discriminating TaqMan PCR. Mucosal cytokine mRNA copy numbers were determined by real time quantitative PCR. Presence of bacterial virulence factors was investigated by cagA, vacAs1/2, and babA2 PCR. Biopsies were assessed with regard to the degrees of granulocytic/lymphocytic infiltration and the presence of intestinal metaplasia (IM) and atrophic gastritis (AG).

Results: Proinflammatory IL-1 polymorphisms (IL-1RN*2(+)/IL-1B-511T/-31C(+)) were associated with increased IL-1beta expression, more severe degrees of inflammation, and an increased prevalence of IM and AG. Carriers of the IL-10-1082G/-819C/-592C alleles (GCC haplotype) had higher mucosal IL-10 mRNA levels than ATA haplotype carriers and were associated with colonisation by more virulent cagA(+), vacAs1(+), and babA2(+) H pylori strains. The TNF-A-307(G/A) and IFN-G+874(A/T) polymorphisms did not influence mucosal cytokine expression or the inflammatory response to H pylori.

Conclusions: Cytokine gene polymorphisms influence mucosal cytokine expression, gastric inflammation, and the long term development of precancerous lesions in H pylori infection. Host polymorphisms are associated with certain bacterial strain types, suggesting host specific colonisation or adaptation. These findings contribute to the understanding of the complex interplay between host and bacterial factors involved in the development of gastric pathology.

Figure 1

Allele/haplotype frequencies of interleukin 10 (IL-10), tumour necrosis factor A (TNF-A), and interferon G (IFN-G) polymorphisms. Single nucleotide polymorphisms (SNPs) at positions −819 and −592 in the IL-10 promoter were in complete linkage disequilibrium (LD). Four IL-10 haplotypes were observed and the occurrence of each haplotype and of haplotype combinations are listed in the shaded boxes.

Figure 2

Interleukin 1β (IL-1β) mRNA amounts in Helicobacter pylori infected patients harbouring different interleukin 1B (IL-1B) and interleukin 1receptor antagonist (IL-1RN) alleles, as well as the proinflammatory IL-1 polymorphism combination IL-1B−511T⁺/IL-1RN2⁺. As IL-1B−511T is in almost complete linkage disequilibrium with IL-1B−31C, data are not shown for the latter single nucleotide polymorphism. Bars within the plots represent median values and numbers above indicate mean IL-1β mRNA amounts for each group. p values were calculated using the Mann-Whitney U test. GAPDH, glyceraldehyde-3-phosphate dehydrogenase.

Figure 3

Interleukin 10 (IL-10) mRNA amounts in Helicobacter pylori infected patients harbouring different IL-10 single nucleotide polymorphism (SNP) alleles (A) and different IL-10 SNP haplotypes/haplotype combinations (B). As the IL-10-592C allele is in complete linkage disequilibrium with IL-10-819C, data are not shown for the latter. Bars within the plots represent median values and numbers above indicate mean IL-10 mRNA amounts for each group. p values were calculated using the Mann-Whitney U test. GAPDH, glyceraldehyde-3-phosphate dehydrogenase.

Figure 4

Prevalence of infection with cagA⁺ and cagA⁻ strains (A), vacAs1⁺ and vacAs1⁻ strains (B), and babA2⁻ and babA2⁺ strains in carriers of different interleukin 10 (IL-10) haplotype combinations (GCC⁻/ATA⁺, low IL-10 secreting haplotype combination; GCC⁺/ATA⁻, high IL-10 secreting haplotype combination). p values were calculated using the χ² test.

Figure 5

Tumour necrosis factor α (TNF-α) and interferon γ (IFN-γ) mRNA amounts in Helicobacter pylori infected patients harbouring different TNF-A−307 and IFN-G−874 alleles. Bars within the plots represent median values and numbers above indicate mean cytokine mRNA amounts for each group. p values were calculated using the Mann-Whitney U test but there were no significant differences between the groups.