title: Role of neutrophils and macrophages in the pathogenesis of necrotizing enterocolitis caused by Cronobacter sakazakii.
abstract: BACKGROUND
  Cronobacter sakazakii (CS) is a highly virulent gram-negative opportunistic pathogen that has been implicated in clinical outbreaks of necrotizing enterocolitis (NEC). The role of mucosal immune cells in CS infection is not well understood. In this study, we sought to elucidate the role of neutrophils (polymorphonuclear leukocytes; PMNs) and macrophages in the pathogenesis of NEC induced by CS using a novel newborn mouse model.
  
  
  METHODS
  PMNs and macrophages were depleted in newborn mice using Gr-1 antibody and carrageenan, respectively, and then infected with 10(3) CFU of CS. The development of NEC in these mice was assessed by a pathologist based on the morphologic changes in the intestine. Cytokine production was determined in the serum and intestinal homogenates of infected mice by enzyme-linked immunosorbent assay (ELISA). Inducible nitric oxide synthase (iNOS) expression and nitric oxide (NO) production was determined by flow cytometry and Greiss method, respectively.
  
  
  RESULTS
  Depletion of PMNs and macrophages in newborn mice led to increased recruitment of dendritic cells (DCs) in the intestine compared with wild-type mice upon infection with CS. PMN- and macrophage-depleted mice showed increased bacterial load, production of pro-inflammatory cytokines, iNOS expression, and NO production in the intestines in comparison to wild-type mice fed with CS. In addition, depletion of PMNs and macrophages prior to infection in mice resulted in severe inflammation, villus destruction, and enhanced enterocyte apoptosis in the intestines compared with CS-infected wild-type mice.
  
  
  CONCLUSIONS
  Our data suggest that depletion of PMNs and macrophages from the lamina propria (LP) exacerbates experimental NEC, indicating that both of these immunocytes play an important role in the clearance of CS during the initial stages of infection. The increased mucosal cytokine response and NO production in the absence of these immunocytes may be responsible for the observed increase in mucosal injury. Understanding how CS manipulates these cells, employing novel mouse model of NEC reported in this study, will provide significant insights for the development of novel therapeutic and preventive strategies to combat NEC.
authors: Department of Surgery, The Saban Research Institute, Children's Hospital Los Angeles, Los Angeles, California, USA.
authors: Claudia N
authors: CN
authors: Emami
authors: Rahul
authors: R
authors: Mittal
authors: Larry
authors: L
authors: Wang
authors: Henri R
authors: HR
authors: Ford
authors: Nemani V
authors: NV
authors: Prasadarao
references: Lancet. 2006 Oct 7;368(9543):1271-83
references: 17027734
references: N Engl J Med. 2011 Jan 20;364(3):255-64
references: 21247316
references: World J Surg. 2002 Jul;26(7):806-11
references: 11948371
references: Infect Immun. 2009 Mar;77(3):1031-43
references: 19075027
references: Nat Immunol. 2005 May;6(5):507-14
references: 15821737
references: PLoS Pathog. 2010 Nov 18;6(11):e1001203
references: 21124939
references: Proc Natl Acad Sci U S A. 1998 Jun 23;95(13):7676-81
references: 9636209
references: Front Biosci (Landmark Ed). 2009 Jan 01;14:4079-102
references: 19273336
references: J Pediatr Surg. 2011 Jan;46(1):81-5
references: 21238645
references: Surg Infect (Larchmt). 2009 Oct;10(5):407-17
references: 19943775
references: Contrib Microbiol. 2008;15:118-146
references: 18511859
references: Pediatr Surg Int. 2009 Apr;25(4):309-18
references: 19301015
references: Annu Rev Immunol. 2002;20:825-52
references: 11861619
references: Semin Pediatr Surg. 2008 May;17(2):98-109
references: 18395659
references: Annu Rev Med. 2009;60:111-24
references: 18817461
references: Am J Pathol. 2010 Mar;176(3):1292-305
references: 20093483
references: Paediatr Perinat Epidemiol. 2002 Oct;16(4):342-9
references: 12445151
references: Pediatr Res. 1993 Dec;34(6):701-8
references: 8108179
references: Cell Microbiol. 2010 Jan;12(1):67-83
references: 19732056
references: Eur Rev Med Pharmacol Sci. 2002 Jan-Feb;6(1):19-25
references: 12608653
references: Microbes Infect. 2003 Nov;5(14):1299-306
references: 14613773
references: JPEN J Parenter Enteral Nutr. 1999 Sep-Oct;23(5 Suppl):S13-7
references: 10483886
references: Lab Invest. 2009 Mar;89(3):263-77
references: 19139724
references: Medicine (Baltimore). 2001 Mar;80(2):113-22
references: 11307587
references: J Clin Microbiol. 2001 Jan;39(1):293-7
references: 11136786
references: Wiley Interdiscip Rev Syst Biol Med. 2009 Nov-Dec;1(3):309-333
references: 20836000
references: Lett Appl Microbiol. 2009 Aug;49(2):153-9
references: 19486285
references: J Immunol. 2009 Nov 15;183(10):6588-99
references: 19846880
references: Paediatr Perinat Epidemiol. 2006 Nov;20(6):498-506
references: 17052286
references: World J Gastroenterol. 2008 Apr 14;14(14):2142-61
references: 18407587