Reduced Expression of UGT1A1 in Intestines of Humanized UGT1 Mice via Inactivation of NF-κB Leads to Hyperbilirubinemia

doi:10.1053/j.gastro.2011.09.045

Gastroenterology

Volume 142, Issue 1, January 2012, Pages 109-118.e2

https://doi.org/10.1053/j.gastro.2011.09.045 Get rights and content

Background & Aims

Bilirubin is a natural and potent antioxidant that accumulates in the blood of newborn children and leads to physiological jaundice. Breastfed infants have higher serum levels of bilirubin than formula-fed infants and are at risk for bilirubin-induced neurological dysfunction (BIND). Clearance of bilirubin requires the expression of uridine diphosphate glucuronosyltransferase (UGT) 1A1; we investigated its role in the association between breast feeding with jaundice in mice.

Methods

We studied mice in which the original Ugt1 locus was disrupted and replaced with the human UGT1 locus (hUGT1 mice); these mice spontaneously develop neonatal hyperbilirubinemia and BIND. We fed human breast milk or formula to neonatal hUGT1 mice and examined activation of the intestinal xenobiotic receptors pregnane X receptor and constitutive androstane receptor. We also examined inflammatory signaling pathways in mice with disruptions in IκB-kinase–α and IκB kinase–β in the intestinal epithelium.

Results

hUGT1 mice that were fed breast milk developed severe hyperbilirubinemia because of suppression of UGT1A1 in the gastrointestinal tract. Formula-fed hUGT1 mice had lower serum levels of bilirubin, which resulted from induction of UGT1A1 in the gastrointestinal tract. hUGT1/Pxr-null mice did not develop severe hyperbilirubinemia, whereas hUGT1/Car-null mice were susceptible to BIND when they were fed breast milk. Breast milk appeared to suppress intestinal IκB kinase α and β, resulting in inactivation of nuclear factor–κB and loss of expression of UGT1A1, leading to hyperbilirubinemia.

Conclusions

Breast milk reduces expression of intestinal UGT1A1, which leads to hyperbilirubinemia and BIND; suppression of this gene appears to involve inactivation of nuclear factor–κB. Hyperbilirubinemia can be reduced by activation of pregnane X receptor, constitutive androstane receptor, or nuclear factor–κB.

Section snippets

Chemicals and Reagents

A mouse anti-human UGT1A1 antibody was a gift of Dr Joseph K. Ritter (Virginia Commonwealth University, Medical College of Virginia, Richmond, VA). Anti–cytochrome P450 (Cyp)2b9/10 antibody and anti-Cyp3a antibody were generously provided by Dr Masahiko Negishi at the National Institute of Environmental Health Sciences and Dr Frank Gonzalez at the National Institutes of Health. Anti–p-glycoprotein (Mdr1) antibody and anti–glyceraldehyde-3 -phosphate dehydrogenase antibody were purchased from

Feeding Suppresses GI UGT1A1 Shortly After Birth

At 5 days after birth, hUGT1 mice are accumulating serum bilirubin and show no detectable human UGT1A1 expression in liver tissue.²⁶ However, UGT1A1 is detected in small intestinal microsomes. With the GI tract playing an important role in bilirubin homeostasis in hUGT1 mice, we examined the levels of UGT1A1 gene expression in the GI tract during embryonic development (E20) just before birth and 8–12 hours after birth. By comparing expression levels before and after birth, it would allow us to

Discussion

Humanized UGT1 mice show little expression of UGT1A1 during neonatal development in the liver, concordant to the reduced expression of bilirubin UGT activity in humans during early development.5, 45 Because control of bilirubin clearance in hUGT1 mice is regulated by intestinal UGT1A1 expression,²⁶ we rationalized that nutritional components originating from breast milk played a key role in controlling the steady-state levels of TSB by regulating intestinal UGT1A1. Although intestinal UGT1A1

Conclusions

Breast feeding has been implicated in short- and long-term health benefits to growing children, which have included reduced risks of infectious diarrhea, necrotizing enterocolitis,⁴⁶ type 1 and type 2 diabetes47, 48; reduced frequency of food allergies⁴⁹; and a protective effect on the development of early-onset inflammatory bowel disease.⁵⁰ With recent findings that bilirubin is a potent and natural antioxidant,¹² the beneficial actions of breast milk can also include its ability to promote

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Subsequently, it was demonstrated that treatments of hUGT1 mice with TCDD, PCN, phenytoin, and fatty acids caused induction of human UGT1A1 in the liver, indicating that the promoter region of human UGT1A1 in hUGT1 mice is responsive to AhR, PXR, and PPAR activations as well [11,34,52]. It was also shown that human UGT1A isoforms expressed in extrahepatic tissues such as small intestine, skin, and brain were inducible by xenobiotics in hUGT1 mice [53–55]. hUGT1 mice were also useful to understand the transcriptional regulation of human UGT1A isoforms in the liver during pregnancy [56].
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: Conflicts of interest The authors disclose no conflicts.

: Funding Funding for this work was provided by US Public Health Service Grants P42ES010337 (R.H.T. and M.K.) and GM086713 (R.H.T.).

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Original ResearchBasic and Translational—Alimentary TractReduced Expression of UGT1A1 in Intestines of Humanized UGT1 Mice via Inactivation of NF-κB Leads to Hyperbilirubinemia

Background & Aims

Methods

Results

Conclusions

Section snippets

Chemicals and Reagents

Feeding Suppresses GI UGT1A1 Shortly After Birth

Discussion

Conclusions

Clin Perinatol

J Biol Chem

J Biol Chem

Pediatr Neurol

Semin Fetal Neonatal Med

Lancet

Atherosclerosis

J Biol Chem

J Biol Chem

J Biol Chem

Cytokine

Biochem Biophys Res Commun

Cancer Cell

Lancet

Lancet

J Pediatr

Management of jaundice and prevention of severe neonatal hyperbilirubinemia in infants > or = 35 weeks gestation

Neonatology

A comparison of alternative risk-assessment strategies for predicting significant neonatal hyperbilirubinemia in term and near-term infants

Pediatrics

Bilirubin UDP-glucuronyltransferase activity in human fetal liver homogenates

Acta Biol Med Ger

The prenatal and postnatal development of UDP-glucuronyltransferase activity towards bilirubin and the effect of premature birth on this activity in the human liver

Biochem J

Imbalance between production and conjugation of bilirubin: a fundamental concept in the mechanism of neonatal jaundice

Pediatrics

Definition of the clinical spectrum of kernicterus and bilirubin-induced neurologic dysfunction (BIND)

J Perinatol

Antioxidant activity of albumin-bound bilirubin

Proc Natl Acad Sci U S A

Diagnosis of kernicterus in the neonatal period

Pediatrics

The protective role of bilirubin in oxygen-radical diseases of the preterm infant

J Perinatol

Original Research
Basic and Translational—Alimentary Tract
Reduced Expression of UGT1A1 in Intestines of Humanized UGT1 Mice via Inactivation of NF-κB Leads to Hyperbilirubinemia