mRNA expression of TLR4, TLR9 and NF-κB in a neonatal murine model of necrotizing enterocolitis

A neonatal model of necrotizing enterocolitis (NEC) in mice was established to examine the role of Toll-like receptors (TLRs) 4 and 9, and of nuclear factor (NF)-κB by quantitative detection of their mRNAs in intestinal tissue during the occurrence of NEC, and thus aid in the understanding of the basic pathogenesis of NEC. A total of 50 newborn BALB/c mice (specific pathogen-free level) ranging in age from 7 to 10 days, of either gender, and weighing 4.8–5.4 g were selected and randomly divided into a control and test group, n=25 mice per group. Mice in the control group were kept in the same cage with the mother who fed them, free from any interventions. Mice in the test group were separated from their mother 48 h following birth and placed in an incubator, artificially fed with milk substitutes, and regularly treated with hypoxia and cold stimulation (100% nitrogen anoxia for 90 sec, cold stimulation at 4°C for 10 min, 3 times a day for 3 days) to induce the neonatal NEC. The general state and body weight variations of the mice were recorded, the mice were sacrificed and the intestinal tissue necrosis was evaluated visually, the degree of intestinal injury was determined by histopathological staining, and the mRNA expression levels of intestinal tissue TLR4, TLR9 and NF-κB were quantified. Of the 25 mice in the test group, 3 died a natural death and 22 were sacrificed; their general state was worse than that of the mice in the control group, and the body weight variations among them were considerably larger. NEC was confirmed in 12 cases by visual inspection, and the average histological scores of the mice in the test group were 3.5±0.6, significantly higher than that in the control group (P<0.05). The mRNA expression of TLR4 and NF-κB in the test group were significantly higher than in the control group. By contrast, the mRNA expression of TLR9 was significantly lower in the test group, and differences were statistically significant (P<0.05). Thus, the increased mRNA expression of TLR4 and NF-κB, and decreased mRNA expression of TLR9 during NEC may be an important inflammatory mechanism of the disease.