Interleukin-1 increases the risk of gastric cancer through induction of aberrant DNA methylation in a mouse model

Interleukin-1 (IL-1) has a significant role in chronic gastric inflammation and manifestations of gastric diseases. The present study aimed to elucidate the specific role of IL-1 in induction of DNA methylation using IL-1 receptor type 1 knockout (IL-1R1(-)/(-)) mice. In the present study, wild-type (WT) and IL-1R1(-)/(-) mice were injected with IL-1 (5 mu g/kg/day). Serum levels of IL-1, interleukin-6 (IL-6) and nitric oxide (NO) were measured by enzyme-linked immunosorbent or NO assays. E-cadherin (E-cad) methylation status and messenger (m)RNA expression of IL-1, IL-6, E-cad and inducible nitric oxide synthase (iNOS) were analyzed. Results from the present study indicated significantly higher IL-1 mRNA expression (P<0.001) in WT mice compared with IL-1R1(-)/(-) mice. IL-1 and IL-6 release was significantly increased in treated WT mice compared with IL-1R1(-)/(-) mice at 1 h, 4 h and 8 h (all P<0.005). IL-1 release was only detected in WT mice following a second dose measured at day 3, week 1 and week 2 when compared with IL-1R1(-)/(-) mice. Promoter methylation of E-cad and a decrease in gene expression was observed in treated WT mice. mRNA expression of iNOS in WT mice was significantly increased at week 1 compared with IL-1R1(-)/(-) mice (P=0.0411). Furthermore, a significantly increased level of NO production was observed in treated WT mice (P<0.005 at 8 h and week 1; P<0.001 at 4 h and day 3) when compared with IL-1R1(-)/(-) mice. The present results indicated that IL-1 was able to directly induce DNA methylation, which may link inflammation-induced epigenetic changes and the development of gastric diseases.