A family of Toll-Like Receptors (TLRs) stimulates the innate immune system upon encountering microbial pattern molecules, lipopolysaccharide [LPS] or peptidoglycans [PG]. When the gastrointestinal tract is initially colonized by microbes at birth, the mucosal innate immune system requires attenuation to avoid chronic inflammation by activation of TLR pathways. In term infants, perinatal downregulation of intestinal TLRs may provide this attenuation. In premature infants born before this developmental regulation, intestinal colonization could activate TLR pathways, leading to chronic inflammation. An inappropriate immune response to bacterial exposure could lead to generalized inflammation and bowel necrosis, such as occurs in necrotizing enterocolitis (NEC). In this proposal, we will study the ontogeny of TLR receptor expression, signaling, and inhibition, and determine its role in regulating innate immune responses. Steroids and probiotic therapy have been shown to prevent the onset of some premature infants predisposed to NEC. The mechanism of steroid action and the role of probiotic therapy will be determined. The probiotic factors that prevent excessive activation of the gut epithelium by microflora in term infants will be identified. The hypothesis is that colonization of the premature infant gut prior to maturation of the TLR signaling pathway can lead to excessive inflammation of the infant gut characteristic of NEC. The capacity of health-promoting probiotic bacteria to accelerate ontogeny of negative regulators of TLR pathways, thereby preventing excessive inflammation, will be investigated. We have developed specific human in-vivo and in-vitro intestinal models for gut inflammation to address this hypothesis.
Our specific aims address whether: (1) coordinated downregulation of TLR receptors and its signaling intermediates and negative regulators prevents excessive inflammatory response to bacterial colonization at birth;(2) pretreatment with glucocorticoids prevents hyperresponsiveness to newly colonizing bacteria by inducing maturation of the TLR signaling pathways in premature gut;and (3) probiotic factors prevent the onset of NEC by accelerating the maturation of the TLR signaling pathways in premature gut. The successful completion of this project will provide novel basic information on the ontogeny of the control elements of TLR signaling pathways, and their modulation by steroids and probiotics. This mechanistic understanding of the effect of steroids and probiotics in preventing inflammation in premature infants could be used to design effective therapeutic strategies to prevent the onset of NEC. This is important since NEC is an important public health issue facing premature infants and accounts for 10% of all deaths in the US.

Public Health Relevance

Despite the recent advances of neonatal intensive care, necrotizing enterocolitis (NEC) remains a major health complication for the premature infants and an important cause of neonatal morbidity and mortality. The major risk factors for NEC are prematurity and bacterial colonization. The proposal is designed to determine the mechanism of inflammation in the premature infants that leads to necrotizing enterocolitis. The proposed TLR-mediated signaling in the immature intestine and the steroids and probiotic therapy may accelerate the maturation of innate immune response preventing the onset of necrotizing enterocolitis. The identification of the mechanism and factors involved in this suppression of inflammation could be of tremendous benefit in understanding and preventing NEC in infants.

National Institute of Health (NIH)
Eunice Kennedy Shriver National Institute of Child Health & Human Development (NICHD)
Research Project (R01)
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Special Emphasis Panel (ZHD1-DSR-A (18))
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Grave, Gilman D
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Massachusetts General Hospital
United States
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Houghteling, Pearl D; Walker, W Allan (2015) Why is initial bacterial colonization of the intestine important to infants' and children's health? J Pediatr Gastroenterol Nutr 60:294-307
Carter, Edward A; Paul, Kasie; Bonab, Ali A et al. (2014) Effect of exercise on burn-induced changes in tissue-specific glucose metabolism. J Burn Care Res 35:470-3
Walker, Allan (2014) Intestinal colonization and programming of the intestinal immune response. J Clin Gastroenterol 48 Suppl 1:S8-11
Wang, Lihong; Cao, Hailong; Liu, Liping et al. (2014) Activation of epidermal growth factor receptor mediates mucin production stimulated by p40, a Lactobacillus rhamnosus GG-derived protein. J Biol Chem 289:20234-44
Weng, Meiqian; Ganguli, Kriston; Zhu, Weishu et al. (2014) Conditioned medium from Bifidobacteria infantis protects against Cronobacter sakazakii-induced intestinal inflammation in newborn mice. Am J Physiol Gastrointest Liver Physiol 306:G779-87
Weng, M; Walker, W A (2013) The role of gut microbiota in programming the immune phenotype. J Dev Orig Health Dis 4:203-14
Nanthakumar, N Nanda; Meng, Di; Newburg, David S (2013) Glucocorticoids and microbiota regulate ontogeny of intestinal fucosyltransferase 2 requisite for gut homeostasis. Glycobiology 23:1131-41
Ganguli, Kriston; Meng, Di; Rautava, Samuli et al. (2013) Probiotics prevent necrotizing enterocolitis by modulating enterocyte genes that regulate innate immune-mediated inflammation. Am J Physiol Gastrointest Liver Physiol 304:G132-41
Rautava, Samuli; Lu, Lei; Nanthakumar, N Nanda et al. (2012) TGF-?2 induces maturation of immature human intestinal epithelial cells and inhibits inflammatory cytokine responses induced via the NF-?B pathway. J Pediatr Gastroenterol Nutr 54:630-8
Rautava, Samuli; Nanthakumar, N Nanda; Dubert-Ferrandon, Alix et al. (2011) Breast milk-transforming growth factor-ýýýýý specifically attenuates IL-1ýý-induced inflammatory responses in the immature human intestine via an SMAD6- and ERK-dependent mechanism. Neonatology 99:192-201

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