Necrotizing enterocolitis (NEC) is the most frequent and the most lethal disease that affects the gastrointestinal tract of the premature infant. The exact etiology of the disease is undefined. The only consistent identifiable epidemiological precursors for NEC are prematurity and enteral alimentation. We have previously shown upregulation of inducible nitric oxide (NO) synthase (NOS-2) mRNA and protein in intestinal segments from infants with acute NEC. NOS-2 colocalized with enterocyte apoptosis and nitrotyrosine immunoreactivity. NOS-2 was downregulated at the time of intestinal stoma closure when the acute inflammation had subsided. We have developed a reproducible model of gut inflammation in neonatal rats thereby simulating the conditions associated with human NEC. We simply formula-feed hypoxic neonatal rats thereby simulating the conditions associated with human NEC. These pups show NOS-2 mRNA upregulation, nitrosative stress, increased enterocyte apoptosis and decreased enterocyte proliferation in the crypts. Intraepithelial lymphocytes (IEL)from hypoxic formula-fed rats secrete more TNF-alpha and IFN- gamma compared to breast-fed rats. In vitro studies suggest that co- culture of IEL with the rat intestinal epithelial cell line IEC-18, in the presence of IL-1beta induces IFN-gamma, TNF-alpha and NOS-2 production which can be abrogated with antibody to IFN-gamma. Furthermore, peroxynitrite (ONOO) induces apoptosis and inhibits proliferation of IEC-6 cells. The data suggest that intestinal necrosis in NEC may be the result of NO-induced imbalance between tissue injury and repair mechanisms. Mucosal injury resulting from perinatal insults leads to bacterial-epithelial interactions, local release of cytokines such as IFN-gamma and TNF-alpha by IEL and lamina propria (LP) lymphocytes. These mediators induce NOS-2 upregulation with production of NO and ONOO by enterocytes or LP macrophages. NO or ONOO in turn promotes further tissue injury (enterocyte apoptosis) and concurrent inhibition of tissue repair mechanisms (enterocyte proliferation) leading to gut barrier failure and NEC. To test our hypothesis, we propose the following Aims: I) To define the mechanism of NOS-2 upregulation in human and experimental rodent NEC. II) To define the mechanisms by which NOS-2 upregulation promotes intestinal injury and alters tissue repair mechanisms in rodent NEC. III) To determine the effects of scavengers of NO or inhibitors of NO production on the development of experimental rodent NEC.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Research Project (R01)
Project #
1R01AI049473-01A1
Application #
6433799
Study Section
Special Emphasis Panel (ZRG1-SSS-W (39))
Program Officer
Rothermel, Annette L
Project Start
2002-02-01
Project End
2007-01-31
Budget Start
2002-02-01
Budget End
2003-01-31
Support Year
1
Fiscal Year
2002
Total Cost
$341,150
Indirect Cost
Name
University of Pittsburgh
Department
Surgery
Type
Schools of Medicine
DUNS #
053785812
City
Pittsburgh
State
PA
Country
United States
Zip Code
15213
Guner, Yigit S; Franklin, Ashanti L; Chokshi, Nikunj K et al. (2011) P-glycoprotein induction by breast milk attenuates intestinal inflammation in experimental necrotizing enterocolitis. Lab Invest 91:1668-79
Wang, J; Ford, H R; Grishin, A V (2010) NF-kappaB-mediated expression of MAPK phosphatase-1 is an early step in desensitization to TLR ligands in enterocytes. Mucosal Immunol 3:523-34
Hunter, Catherine J; Williams, Monica; Petrosyan, Mikael et al. (2009) Lactobacillus bulgaricus prevents intestinal epithelial cell injury caused by Enterobacter sakazakii-induced nitric oxide both in vitro and in the newborn rat model of necrotizing enterocolitis. Infect Immun 77:1031-43
Hunter, Catherine Jane; Ford, Henri R; Estrada, Joaquin J et al. (2009) Alpha-fetoprotein levels correlate with the pathologic grade and surgical outcomes of pediatric retroperitoneal teratomas. Pediatr Surg Int 25:331-6
Wang, Jin; Ouyang, Yannan; Guner, Yigit et al. (2009) Ubiquitin-editing enzyme A20 promotes tolerance to lipopolysaccharide in enterocytes. J Immunol 183:1384-92
Hunter, Catherine J; Singamsetty, Vijay K; Chokshi, Nikunj K et al. (2008) Enterobacter sakazakii enhances epithelial cell injury by inducing apoptosis in a rat model of necrotizing enterocolitis. J Infect Dis 198:586-93
Hunter, C J; Chokshi, N; Ford, H R (2008) Evidence vs experience in the surgical management of necrotizing enterocolitis and focal intestinal perforation. J Perinatol 28 Suppl 1:S14-7
Chokshi, Nikunj K; Guner, Yigit S; Hunter, Catherine J et al. (2008) The role of nitric oxide in intestinal epithelial injury and restitution in neonatal necrotizing enterocolitis. Semin Perinatol 32:92-9
Hunter, Catherine J; Upperman, Jeffrey S; Ford, Henri R et al. (2008) Understanding the susceptibility of the premature infant to necrotizing enterocolitis (NEC). Pediatr Res 63:117-23
Cetin, Selma; Leaphart, Cynthia L; Li, Jun et al. (2007) Nitric oxide inhibits enterocyte migration through activation of RhoA-GTPase in a SHP-2-dependent manner. Am J Physiol Gastrointest Liver Physiol 292:G1347-58

Showing the most recent 10 out of 18 publications