Neonatal Necrotizing Enterocolitis: Clinical Considerations and Pathogenetic Concepts
Tóm tắt
Necrotizing enterocolitis (NEC), a disease affecting predominantly premature infants, is a leading cause of morbidity and mortality in neonatal intensive care units. Although several predisposing factors have been identified, such as prematurity, enteral feeding, and infection, its pathogenesis remains elusive. In the past 20 years, we have established several animal models of NEC in rats and found several endogenous mediators, especially platelet-activating factor (PAF), which may play a pivotal role in NEC. Injection of PAF induces intestinal necrosis, and PAF antagonists prevent the bowel injury induced by bacterial endotoxin, hypoxia, or challenge with tumor necrosis factor-α (TNF) plus endotoxin in adult rats. The same is true for lesions induced by hypoxia and enteral feeding in neonatal animals. Human patients with NEC show high levels of PAF and decreased plasma PAF-acetylhydrolase, the enzyme degrading PAF. The initial event in our experimental models of NEC is probably polymorphonuclear leukocyte (PMN) activation and adhesion to venules in the intestine, which initiates a local inflammatory reaction involving proinflammatory mediators including TNF, complement, prostaglandins, and leukotriene C4. Subsequent norepinephrine release and mesenteric vasoconstriction result in splanchnic ischemia and reperfusion. Bacterial products (e.g., endotoxin) enter the intestinal tissue during local mucosal barrier breakdown, and endotoxin synergizes with PAF to amplify the inflammation. Reactive oxygen species produced by the activated leukocytes and by intestinal epithelial xanthine oxidase may be the final pathway for tissue injury. Protective mechanisms include nitric oxide produced by the constitutive (mainly neuronal) nitric oxide synthase, and indigenous probiotics such as Bifidobacteria infantis. The former maintains intestinal perfusion and the integrity of the mucosal barrier, and the latter keep virulent bacteria in check. The development of tissue injury depends on the balance between injurious and protective mechanisms.
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Tài liệu tham khảo
Benirschke K., 1974, Necrotizing Enterocolitis in the Newborn Infant: Report of the 68th Ross Conference on Pediatric Research., 29
deSa DJ, 1976, Perspect Pediatr Pathol, 3, 273
Sechi LA, 1993, Am J Physiol, 265, G21
Crissinger KD, 1981, Am J Physiol, 130, 537
Gonzalez-Crussi F, 1983, The role of platelet-activating factor and endotoxin. Am J Pathol, 112, 127
Hsueh W, 1986, An investigation of secondary mediators in its pathogenesis. Am J Pathol, 122, 231
Brown EG, 1980, Neonatal Necrotizing Enterocolitis., 69
Benveniste J., 1988, Prog Clin Biol Res, 282, 73
Handley DA, 1990, Platelet-Activating Factor in Endotoxin and Immune Diseases., 451
Toth PD, 1990, Platelet-Activating Factor in Endotoxin and Immune Diseases., 589
Zanetti G, 1992, Comparative protective efficacy of antibodies to tumor necrosis factor-alpha and to lipopolysaccharide. J Immunol, 148, 1890
Lloberas N, 2002, Prevention by antioxidant treatment. FASEB J, 16, 908
Sun XM, 1996, Am J Physiol, 270, G184
Kubes P, 1990, Am J Physiol, 258, G158
Sun X, 1997, Am J Physiol, 273, G56
Granger DN, 1988, Am J Physiol, 255, H1269
Jaattela M., 1991, Lab Invest, 64, 724
Vilcek J, 1991, New insights into the molecular mechanisms of its multiple actions. J Biol Chem, 266, 7313
Hsueh W, 1990, Immunology, 70, 309
Huang L, 1994, Immunology, 83, 65
Tan XD, 1993, TNF gene expression in Paneth cells, intestinal eosinophils and macrophages. Am J Pathol, 142, 1858
Nevalainen TJ, 1995, Lab Invest, 72, 201
Baeuerle PA, 1991, Biochim Bio-phys Acta, 1072, 63
De Plaen IG, 2002, Pediatr Res, 51, 139A
Sun X, 1995, Roles of TNF, complement activation and endogenous PAF production. Dig Dis Sci, 40, 495
Siren AL, 1989, Am J Physiol, 257, H25
Hsueh W, 1988, A mechanistic study of platelet-activating factor-induced bowel necrosis. Gastroenterology, 94, 1412
Pitt J, 1977, 1. Role of milk leukocytes. Pediatr Res, 11, 906
Barlow B, 1975, Surgery, 77, 687
Vadas P, 1993, Circ Shock, 39, 160
Amer MD, 1994, Clin Res, 42, 372A
Farr RS, 1983, Fed Proc, 42, 3120