Submitted on April 16, 2007
Accepted on October 17, 2007
Decreased Development of Necrotizing Enterocolitis in IL-18 Deficient Mice
Melissa D. Halpern1*, Ludmila Khailova1, Dania Molla Hosseini1, Kelly M Arganbright1, Charity A Reynolds1, Masako Yajima2, Junji Hoshiba3, and Bohuslav Dvorak1
1 Pediatrics, University of Arizona, Tucson, Arizona, United States
2 Department of Lactic Acid Bacteria, Food Science Institute, Division of Research and Development, Meiji Dairies Corporation, Tokyo, Japan
3 Department of Animal Resources, Advanced Science Research Center, Okayama University, Okayama, Japan
* To whom correspondence should be addressed. E-mail: mhalpern{at}peds.arizona.edu.
Necrotizing enterocolitis (NEC) is a devastating gastrointestinal disease of prematurely born infants, characterized in its severest from by hemorrhagic inflammatory necrosis of the distal ileum and proximal colon. Pro-inflammatory cytokines have been implicated in the development of NEC and we have previously shown that IL-18 is significantly elevated in the neonatal rat model of NEC. To determine if IL-18 contributes to intestinal pathology in NEC, we subjected IL-18 knockout mice to the protocol used to develop experimental NEC in newborn rats. Newborn B6.129P2-Il18tm1Aki/J (NEC IL-18 -/-) and wild-type (NEC WT) mice were hand fed every 3 hours with cow's milk-based formula and exposed to asphyxia and cold stress twice daily. After 72 hours, animals were sacrificed and ileum and liver were removed. Disease development was determined via histological changes in the ileum scored by a blinded evaluator. The number of TNF-
, IL-12 and IL-1
positive cells and macrophages were determined in ileum and liver via immunohistology. I
B- and IB- were determined from protein extracts from ileum and liver using Western blot. The incidence and severity of NEC was significantly reduced in NEC IL-18 -/- mice compared to controls. Further, mean ileal macrophages and hepatic IL-1 were significantly reduced in IL-18 -/- mice subjected to the NEC protocol. There were no statistically significant changes in Kupffer cells, hepatic TNF-, ileal IL-1 or IL-12. IB- and IB- were significantly increased in NEC IL-18 -/- mice ileum and liver, respectively. These results confirm that IL-18 plays a crucial role in experimental NEC pathogenesis.
