Uridine Diphospho-glucuronosyl Transferase 1A1 Research Articles

Kinetic Characterization of Estradiol Glucuronidation by Liver Microsomes and Expressed UGT Enzymes: The Effects of Organic Solvents.

In vitro glucuronidation of 17β-estradiol (estradiol) is often performed to assess the role of uridine 5'-diphospho-glucuronosyltransferase 1A1 (UGT1A1) in xenobiotic/drug metabolism. The objective of this study was to determine the effects of four commonly used organic solvents [i.e., dimethyl sulfoxide (DMSO), methanol, ethanol, and acetonitrile] on the glucuronidation kinetics of estradiol, which can be glucuronidated at C3 and C17 positions. The impacts of organic solvents on estradiol glucuronidation were determined by using expressed UGT enzymes and liver microsomes from both human and animals. In human liver microsomes (HLM), methanol, ethanol, and acetonitrile significantly altered estradiol glucuronidation kinetics with increased Vmax (up to 2.6-fold) and CLmax (up to 2.8-fold) values. Altered estradiol glucuronidation in HLM was deduced to be attributed to the enhanced metabolic activities of UGT1A1 and UGT2B7, whose activities differ at the two glucuronidation positions. The effects of organic solvents on estradiol glucuronidation were glucuronidation position-, isozyme-, and solvent-specific. Furthermore, both ethanol and acetonitrile have a greater tendency to modify the glucuronidation activity of estradiol in animal liver microsomes. Organic solvents such as methanol, ethanol, and acetonitrile showed great potential in adjusting the glucuronidation of estradiol. DMSO is the most suitable solvent due to its minimal influence on estradiol glucuronidation. Researchers should be cautious in selecting appropriate solvents to get accurate results when assessing the metabolism of a new chemical entity.

Do Gene Polymorphisms Play a Role in Newborn Hyperbilirubinemia?

Polymorphisms of the uridine-diphospho-glucuronosyltransferase 1A1 (UGT1A1) gene, hepatic solute carrier organic anion transporter 1B1/B3 (SLCO1B1/3) gene, and glutathione S-transferase (GST) gene have been associated with significant hyperbilirubinemia in some populations. This study aims to determine whether the variation of UGT1A1, SLCO1B1/3 and GST genes play an important role in neonatal hyperbilirubinemia in Turkish newborn infants. The study included 61 idiopathic hyperbilirubinemia cases, 28 prolonged jaundice cases, and 41 controls. Ten common polymorphisms in four genes involved in bilirubin metabolism were examined. Polymerase chain reaction-restriction fragment length polymorphism method was used to detect variants of those genes. No association was found between the variants of UGT1A1 at nt 211, the SLCO1B1 gene at nt 388, 463, 521, 1463, the SLCO1B3 gene at nt 334, 727+118, 1865+19721, and the GST gene at nt 313, 341, and neonatal hyperbilirubinemia. There was no difference between the case and control groups in terms of allele frequencies of these genes (except SLCO1B3 at nt 334) (p>0.05 in all comparisons). The presence of the G allele of the SLCO1B3 at nt 334 variant gene seemed to protect from jaundice in infants with idiopathic hyperbilirubinemia. These gene polymorphisms currently studied do not seem to modulate the risk of hyperbilirubinemia in Turkish newborn infants.

Polymorphisms in gene UGT1A1 modify the association of prenatal exposure to polycyclic aromatic hydrocarbons with congenital heart diseases risk

Introduction Prenatal exposure to polycyclic aromatic hydrocarbons (PAHs) is a risk factor for the occurrence of congenital heart diseases (CHDs). Genetic susceptibility to PAHs metabolism may modify the exposure–risk relationship. The role of uridine diphosphoglucuronosyl transferase 1A1 (UGT1A1) genetic polymorphisms for modulating the impacts of prenatal PAHs exposure on the risk of CHDs remains to be discovered. Objective The aim of this study was to investigate whether maternal UGT1A1 genetic polymorphisms are associated with fetal susceptibility to CHDs and to assess whether the risk is modified by maternal PAHs exposure. Methods Maternal urinary biomarker of PAHs exposure was determined in 357 pregnant women with CHDs fetuses and 270 controls (pregnant women carrying fetuses without major congenital malformations). Urinary 1-hydroxypyrene-glucuronide (1-OHPG) concentration, a sensitive biomarker for PAHs exposure, was measured using ultra-high-performance liquid chromatography coupled with tandem mass spectrometry. Maternal single nucleotide polymorphisms (SNPs) in UGT1A1, including rs3755319, rs887829, rs4148323, rs6742078, and rs6717546, were genotyped using an improved multiplex ligation detection reaction (iMLDR) technique. Unconditional logistic regression was performed to determine the impacts of UGT1A1 polymorphisms on the risks of CHDs and their subtypes. Generalized multifactor dimensionality reduction (GMDR) was used to analyze the gene–gene and gene–PAHs exposure interactions. Results None of the selected UGT1A1 polymorphisms was independently associated with the risk of CHDs. The interaction between SNP rs4148323 and PAHs exposure was observed to be associated with CHDs (p< .05). Pregnant women with high-level PAHs exposure and rs4148323 had an increased risk of carrying CHDs fetuses (GA-AA vs. GG: aOR = 2.00, 95% CI = 1.06–3.79). Moreover, the joint effect of rs4148323 and PAHs exposure was found to be significantly associated with risks of septal defects, conotruncal heart defects, and right-sided obstructive malformations. Conclusions Maternal genetic variations of UGT1A1 rs4148323 may modify the association between prenatal PAHs exposure and CHDs risk. This finding needs to be further confirmed in a larger-scale study.

Equine uridine diphospho-glucuronosyltransferase 1A1, 2A1, 2B4, 2B31: cDNA cloning, expression and initial characterization of morphine metabolism

ObjectiveUridine diphospho-glucuronosyltransferases (UGTs) are membrane-bound enzymes that catalyze the conjugation of glucuronic acid onto a diverse set of xenobiotics. Horses efficiently and extensively glucuronidate a number of xenobiotics, including opioids, making UGTs an important group of drug-metabolizing enzymes for the clearance of drugs. Recombinant enzymes have allowed researchers to characterize the metabolism of a variety of drugs. The primary objective was to clone, express and characterize equine UGTs using drugs characterized as UGT substrates in other species. A secondary objective was to characterize the in vitro metabolism of morphine in horses. Study designIn vitro drug metabolism study using liver microsomes and recombinant enzyme systems. AnimalsLiver microsomes and RNA from tissue collected from two Thoroughbred mares euthanized for other reasons. MethodsBased on homology to the human UGT2B7, four equine UGT variants were expressed: UGT1A1, UGT2A1, UGT2B31 and UGT2B4. cDNA sequences were cloned and resulting protein expressed in a baculovirus expression system. Functionality of the enzymes was assessed using 4-methylumbelliferone, testosterone, diclofenac and ketoprofen. Recombinant enzyme, control cells, equine liver microsomes and human UGT2B7 supersomes were then incubated with morphine. Concentrations of metabolites were measured using liquid chromatography–tandem mass spectrometry and enzyme kinetics determined. Results4-Methylumbelliferone was glucuronidated by all expressed equine UGTs. Testosterone glucuronide was not produced by any of the expressed enzymes, and diclofenac glucuronide and ketoprofen glucuronide were produced by UG2A1 and UGT1A1, respectively. UGT2B31 metabolized morphine to morphine-3-glucuronide and low concentrations of morphine-6-glucuronide. Conclusions and clinical relevanceThis is the first successful expression of functional recombinant equine UGTs. UGT2B31 contributes to the glucuronidation of morphine; however, it is probably not the main metabolizing enzyme. These results warrant further investigation of equine UGTs, including expression of additional enzymes and further characterization of UGT2B31 as a contributor to morphine metabolism.

Combined Effects of UGT1A1 and SLCO1B1 Variants on Chinese Adult Mild Unconjugated Hyperbilirubinemia.

The potential for genetic variation to cause adult unconjugated hyperbilirubinemia is increasingly being recognized. However, the cumulative effects of genetic variants have not been fully illuminated. The current study aimed to investigate the effects of uridine diphospho-glucuronosyl transferase 1A1 (UGT1A1) and/or solute carrier organic anion transporter family member 1B (SLCO1B) polymorphic variants and their combined effects on mild unconjugated hyperbilirubinemia in Chinese adults. Fourteen genetic variants in the UGT1A1 or SLCO1B gene were genotyped through sequencing in 148 adults with unconjugated hyperbilirubinemia and 158 healthy controls. Variants c.-3275T > G, (TA)6>(TA)7, c.211G > A or c.1091C > T within the UGT1A1 gene as well as c.521T > C within the SLCO1B1 gene appear to be genetic risk factors for inherited unconjugated hyperbilirubinemia. After adjusting for covariates, the results of multivariate logistic regressions revealed that odds ratios (ORs) [(with 95% confidence interval (CI)] of these five variants were 2.35 (95% CI: 1.37–4.01, p = 0.002), 2.38 (95% CI: 1.35–4.20, p = 0.003), 2.99 (95% CI: 1.71–5.21, p < 0.001), 7.60 (95% CI: 1.99–28.96, p = 0.003), and 2.54 (95% CI: 1.27–5.11, p = 0.009), respectively. The OR for unconjugated hyperbilirubinemia is positively correlated with the cumulative number of these five variants in adults. And the greater the number of genetic variations, the higher the total bilirubin level. Adults carrying diplotype 3/4 (homozygous c.-3275T > G and heterozygous (TA)6>(TA)7) had higher bilirubin levels than those with diplotypes 1/3 (heterozygous c.-3275T > G and (TA)6>(TA)7)) or 1/4 (heterozygous c.-3275T > G) (P < 0.05). Similarly, bilirubin levels in individuals with diplotype 2/4 (heterozygous c.-3275T > G and c.211G > A) were higher than adults carrying diplotypes 1/2 (heterozygous c.211G > A) or 1/4 (P < 0.001). For subjects with heterozygous or homozygous variant c.211G> A, as the number of c.521T > C alleles variation increased, the incidence of unconjugated hyperbilirubinemia increased, but it was not statistically significant. Our results indicate that variants of UGT1A1 and/or SLCO1B1 have combined effects on Chinese adult mild unconjugated hyperbilirubinemia.

Mechanism of the efflux transport of demethoxycurcumin-O-glucuronides in HeLa cells stably transfected with UDP-glucuronosyltransferase 1A1

Demethoxycurcumin (DMC) is a safe and natural food-coloring additive, as well as an agent with several therapeutic properties. However, extensive glucuronidation in vivo has resulted in its poor bioavailability. In this study, we aimed to investigate the formation of DMC-O-glucuronides by uridine 5'-diphospho-glucuronosyltransferase 1A1 (UGT1A1) and its transport by breast cancer resistance protein (BCRP) and multidrug resistance-associated proteins (MRPs) in HeLa cells stably transfected with UGT1A1 (named HeLa1A1 cells). The chemical inhibitors Ko143 (a selective BCRP inhibitor) and MK571 (a pan-MRP inhibitor) both induced an obvious decrease in the excretion rate of DMC-O-glucuronides and a significant increase in intracellular DMC-O-glucuronide concentrations. Furthermore, BCRP knock-down resulted in a marked reduction in the level of excreted DMC-O-glucuronides (maximal 55.6%), whereas MRP1 and MRP4 silencing significantly decreased the levels of excreted DMC-O-glucuronides (a maximum of 42.9% for MRP1 and a maximum of 29.9% for MRP3), respectively. In contrast, neither the levels of excreted DMC-O-glucuronides nor the accumulation of DMC-O-glucuronides were significantly altered in the MRP4 knock-down HeLa cells. The BCRP, MRP1 and MRP3 transporters were identified as the most important contributors to the excretion of DMC-O-glucuronides. These results may significantly contribute to improving our understanding of mechanisms underlying the cellular disposition of DMC via UGT-mediated metabolism.

The effect of excision repair cross complementing 1 and thymidylate synthetase mRNA expression and uridine-diphosphoglucuronosyl transferase 1A1 gene polymorphism on chemotherapeutic effect and prognosis of gastric cancer

Objective To analyze the impact of excision repair cross complementation group 1 (ERCC1), thymidylate synthetase (TYMS) mRNA expression, and uridine-diphosphoglucuronosyl transferase 1A1 (UGT1A1)*28/*6 gene polymorphisms on chemoresponse and clinical outcome of patients with colorectal cancer treated with fluorouracil combined with oxaliplatin (FOLFOX) or fluorouracil combined with irinotecan (FOLFIRI) regimen. Methods Among the 96 patients with gastric cancer, 47 patients were treated with FOLFOX regimen, and 49 patients underwent neoadjuvant chemotherapy with FOLFIRI regimen. The gene expression of gastric cancer patients was analyzed, and the chemotherapy efficacy and prognosis of the two groups were observed. Results Chemotherapy remission rate (72.4%, 57.9%) in patients with low expression of ERCC1 and TYMS, median disease progression time (12.6, 16.9 months), median overall survival time (26.4, 23.8 months, respectively) were significantly better than those in patients with high expression of ERCC1 and TYMS (38.9%, 34.5%) and median disease progression. Time (7.9, 12.3 months respectively) and median total survival (15.7, 16.2 months respectively) were significantly different (P 0.05). In addition, there was no significant difference in the efficacy of chemotherapy between *28 and *6 genotypes (P>0.05). Conclusion The gene expression of gastric cancer patients was analyzed, and the chemotherapy efficacy and prognosis of the two groups were observed. Key words: Colorectal cancer; Excision repair cross complementing 1; Thymidylate synthetase; Uridine-diphosphoglucuronosyl transferase 1A1; Chemoresistence

Systemic regulation of bilirubin homeostasis: Potential benefits of hyperbilirubinemia.

Neurotoxic bilirubin is the end product of heme catabolism in mammals. Bilirubin is solely conjugated by uridine diphospho-glucuronosyltransferase 1A1, which is a membrane-bound enzyme that catalyzes the transfer of glucuronic acid. Due to low function of hepatic and intestinal uridine diphospho-glucuronosyltransferase 1A1 during the neonatal period, human neonates develop mild to severe physiological hyperbilirubinemia. Accumulation of bilirubin in the brain leads to the onset of irreversible brain damage, termed kernicterus. Breastfeeding is one of the most significant factors that increase the risk of developing kernicterus in infants. Why does this most natural way of feeding increase the risk of brain damage or even death? This question leads to the hypothesis that breast milk-induced hyperbilirubinemia might bring certain benefits that outweigh those risks. While bilirubin is neurotoxic and cytotoxic, this compound is also a potent antioxidant. There are studies showing improved clinical conditions in patients with hyperbilirubinemia. Accumulating evidence also shows that genetic polymorphisms linked to hyperbilirubinemia are beneficial against various diseases. In this review article, we first introduce the production, metabolism, and transport of bilirubin. We then discuss the potential benefits of neonatal and adult hyperbilirubinemia. Finally, epigenetic factors as well as metabolomic information associated with hyperbilirubinemia are described. This review article advances the understanding of the physiological importance of the paradoxical compound bilirubin. (Hepatology 2018;67:1609-1619).

Genetic polymorphisms of UGT1A1 and susceptibility to anti-tuberculosis drug-induced liver: A RUCAM-based case–control study

Uridine 5’-diphospho-glucuronosyl-transferase 1A1 (UGT1A1) plays an important role in the biliary excretion of bilirubin, suggesting genetic polymorphisms of UGT1A1 may have an impact on bile acid metabolism, which may be related to the development of anti-tuberculosis drug-induced liver injury (ATLI). This study explores the associations between genetic polymorphisms of UGT1A1 and ATLI in a Chinese anti-tuberculosis population. A 1:2 matched case–control study was conducted among 290 ATLI cases and 580 controls, of which causality assessment of ATLI cases was based on the updated Roussel Uclaf Causality Assessment Method (RUCAM). Conditional logistic regression was applied to calculate odds ratio (OR) and 95% confidence intervals (CIs), with weight and use of hepatoprotectant as covariates. The Bonferroni correction was used to adjust P values for multiple testing. Compared with those carrying rs6719561 TT genotype, patients with TC genotype had lower risk of ATLI (adjusted OR = 0.723, 95% CI: 0.531–0.985, P = 0.040). The haplotype TAG (rs3755319-rs2003569-rs4148323) could marginally significantly increase the risk of ATLI (adjusted OR = 5.071, 95% CI: 1.007–25.531, P = 0.049), while haplotype TC (rs4148329-rs6719561) could reduce the risk of ATLI (adjusted OR = 0.719, 95% CI: 0.527–0.982, P = 0.038). Patients with polymorphisms at rs4148328 or rs3755319 were at a reduced risk of moderate and severe liver injury under different genetic models. Based on this case–control study, genetic polymorphisms of UGT1A1 may be associated with susceptibility to ATLI in the Chinese anti-tuberculosis population.

Detection of UGT1A1*28 Polymorphism Using Fragment Analysis

背景与目的尿苷二磷酸葡萄糖醛酸转移酶（uridine diphosphate glucuronosyl transferase 1A1, UGT1A1）是伊立替康代谢最主要的同工酶，UGT1A1基因的多态性影响UGT1A1的活性，本研究建立片段分析法检测UGT1A1*28 TATA盒的多态性。方法调取2014年4月-2015年5月在广东省人民医院的住院肺癌患者库存血液标本286例，建立片段分析法检测UGT1A1*28 TATA多态性，与Sanger测序方法比较其精确度和准确度。结果286例肿瘤血液中，UGT1A1*28 TATA盒TA6/6型有236例（82.5%），TA6/7型有48例（16.8%），TA7/7型2例（0.7%）。片段分析法与Sanger测序法比较，精确度与准确度达100%。结论片段分析法适用于临床检测UGT1A1*28多态性，成本低且方便快捷。

A cross-sectional clinic-based study exploring whether variants within the glutathione S-transferase, haptoglobin and uridine 5'-diphospho-glucuronosyltransferase 1A1 genes are associated with interindividual phenotypic variation in sickle cell anaemia in Jamaica.

To explore putative associations between specific variants in either the glutathione S-transferase (GST), haptoglobin (HP) or uridine 5'-diphospho-glucuronosyltransferase 1A1 (UGT1A1) genes and clinically important phenotypes in sickle cell anaemia (HbSS). 371 HbSS participants were recruited from the Sickle Cell Clinic of the Sickle Cell Unit at the University of the West Indies, Kingston, Jamaica. Markers within four GST superfamily genes, the HP gene and the UGT1A1 gene were analysed using PCR-based assays. Multivariable regression revealed statistically significant associations between the GSTP1 Ile105Val heterozygote and HbA2 levels (P=.016), HbF percentage (P=.001), MCH concentration (P=.028) and reticulocyte count (P=.032), while the GSTM3 D/D homozygote was significantly associated with HbA2 levels (P=.032). The UGT1A1 (TA)6 /(TA)8 heterozygote showed statistically significant associations with HbA2 levels (P=.019), HbF percentage (P<.001), haemoglobin levels (P=.008), PCV values (P=.007) and RBC counts (P=.041). This exploratory cross-sectional study has generated novel and informative genotype-phenotype estimates of association, but larger studies are needed to determine whether these specific variants within the GST, UGT1A1 and HP genes are related to interindividual phenotypic variability in HbSS.

AM-2201 Inhibits Multiple Cytochrome P450 and Uridine 5'-Diphospho-Glucuronosyltransferase Enzyme Activities in Human Liver Microsomes.

AM-2201 is a synthetic cannabinoid that acts as a potent agonist at cannabinoid receptors and its abuse has increased. However, there are no reports of the inhibitory effect of AM-2201 on human cytochrome P450 (CYP) or uridine 5′-diphospho-glucuronosyltransferase (UGT) enzymes. We evaluated the inhibitory effect of AM-2201 on the activities of eight major human CYPs (1A2, 2A6, 2B6, 2C8, 2C9, 2C19, 2D6, and 3A4) and six major human UGTs (1A1, 1A3, 1A4, 1A6, 1A9, and 2B7) enzymes in pooled human liver microsomes using liquid chromatography–tandem mass spectrometry to investigate drug interaction potentials of AM-2201. AM-2201 potently inhibited CYP2C9-catalyzed diclofenac 4′-hydroxylation, CYP3A4-catalyzed midazolam 1′-hydroxylation, UGT1A3-catalyzed chenodeoxycholic acid 24-acyl-glucuronidation, and UGT2B7-catalyzed naloxone 3-glucuronidation with IC50 values of 3.9, 4.0, 4.3, and 10.0 µM, respectively, and showed mechanism-based inhibition of CYP2C8-catalyzed amodiaquine N-deethylation with a Ki value of 2.1 µM. It negligibly inhibited CYP1A2, CYP2A6, CYP2B6, CYP2C19, CYP2D6, UGT1A1, UGT1A4, UGT1A6, and UGT1A9 activities at 50 μM in human liver microsomes. These in vitro results indicate that AM-2201 needs to be examined for potential pharmacokinetic drug interactions in vivo due to its potent inhibition of CYP2C8, CYP2C9, CYP3A4, UGT1A3, and UGT2B7 enzyme activities.

Effect of genetic variants of bilirubin metabolism on the degree of hyperbilirubinemia in African-American newborns.

The objective of our study was to measure the effect of genetic variants of these two enzymes, UGT1A1 and SLCO1B1, in the bilirubin metabolic pathway on the degree of hyperbilirubinemia in a cohort of African-American (AA) infants from our well-baby nursery. In addition, a second objective was to document the types and frequencies of genetic variations of these enzymes in our cohort. A prospective study of 180 AA infants from the Well Baby Nursery of an inner city community hospital, all of whose mothers were type O pos. Sixty infants were ABO-incompatible direct antiglobulin test (DAT) pos, 60 were ABO-incompatible DAT neg and 60 were type O+. Blood for carboxyhemoglobin (COHb) and variants of the enzymes uridine diphosphoglucuronosyltransferase 1A1 and hepatic solute carrier organic anion transporter 1B1 (SLCO1B1) was drawn at the time of the infants' initial bilirubin, and the infants' precise percentile on the Bhutani nomogram was calculated. Variants in the two enzymes studied were quite common. In total, 21.1% were positive for a Gilbert phenotype, whereas an additional 42.4% were heterozygous for the *28 or *37 variant of UGT1A1. In total, 67.2% were homozygous for the *60 variant of the phenobarbital responsive enhancer module. In total, 41.1% were homozygous for the *1b variant of SLCO1B1, whereas an additional 12.7% were positive for the *4 variant of this gene. In total, 20.6% of infants had variations in both genes. Using logistic regression when COHbc was assessed with each of the different variants, only COHbc (P<0.0001 to 0.0004) was significantly associated with the level of hyperbilirubinemia as defined by the Bhutani nomogram. Although we have found quite a large number of genetic variants of the UGT1A1 and SLCO1B1 genes in the AA population, it does not appear that they have a significant impact on the incidence of hyperbilirubinemia among this group of infants.

S30 - Can irinotecan dose reduction according to ugt1a1 genotype avoid severe toxicities?

Background: Uridine diphosphoglucuronosyl transferase 1A1 (UGT1A1) *28 polymorphism reduces UGT1A1 enzymatic activity and is possibly associated with irinotecan(IRI)-induced neutropenia and diarrhea. The aim of this single-centre analysis is to assess if IRI dose-reduction according to UGT1A1 status can avoid severe toxicities. Patients and methods: Patients (pts) with different solid tumours candidate to chemotherapy with IRI were consecutively genotyped for UGT1A1*28 polymorphism at our Institution. DNA was extracted from peripheral blood cells and UGT1A1 promoter region was amplified with PCR, using primers marked with a fluorochrome; a specific kit prepared in our laboratories was used. Data about clinico-pathological features, IRI dose reduction, toxicity, objective response rate and progression free survival were retrospectively collected. Results: From January 2015 to March 2016, 122 pts were genotyped for UGT1A1 (M/F 59/63, median age 67): 39% were omozygous wild-type, 48% were heterozygous, 13% were omozygous mutated. At the time of our analysis IRI was administered to 32 pts with the following characteristics: M/F 13/19; median age 62.5 (range 38-85); colorectal cancer/pancreatic cancer/gastroesophageal cancer 23/7/2; UGT1A1 wild-type/heterozygous/omozygous 10/16/6. The median IRI-starting dose was 180 mg/mq in wild-type group, 135 mg/mq in heterozygous group and 135 mg/mq in omozygous group. A correlation between UGT1A1 homozygosis and G3-4 toxicity was observed (chi2 = 0.042). After the first cycle, grade = 3 neutropenia occurred in 2 pts in the omozygous group, grade = 3 diarrhea occurred in 1 wild-type and in 1 omozygous patient. 2 of the omozygous pts who experienced high grade toxicities had received high-doses of IRI (180 mg/mq). Response to treatment was evaluated in 19 pts: 3 partial responses, 6 stable diseases and 10 progressive diseases were observed. At the time of analysis 16 pts had progressed with a median progression free survival of 4.2 months, but data are still immature for further survival analysis. Conclusions: UGT1A1 genotype can be used to individualize IRI-dosage in order to reduce treatment related high-grade neutropenia and diarrhea in mutated pts. Further studies and longer follow-up are needed to assess the safer IRI-dosage in both omozygous and heterozygous mutated pts and to evaluate the efficacy of dose-reduction in terms of response to treatment and survival.

Role of brain cytochrome P450 mono-oxygenases in bilirubin oxidation-specific induction and activity.

In the Crigler-Najjar type I syndrome, the genetic absence of efficient hepatic glucuronidation of unconjugated bilirubin (UCB) by the uridine 5'-diphospho-glucuronosyltransferase1A1 (UGT1A1) enzyme produces the rise of UCB level in blood. Its entry to central nervous system could generate toxicity and neurological damage, and even death. In the past years, a compensatory mechanism to liver glucuronidation has been indicated in the hepatic cytochromes P450 enzymes (Cyps) which are able to oxidize bilirubin. Cyps are expressed also in the central nervous system, the target of bilirubin toxicity, thus making them theoretically important to confer a protective activity toward bilirubin accumulation and neurotoxicity. We therefore investigated the functional induction (mRNA, EROD/MROD) and the ability to oxidize bilirubin of Cyp1A1, 1A2, and 2A3 in primary astrocytes cultures obtained from two rat brain region (cortex: Cx and cerebellum: Cll). We observed that Cyp1A1 was the Cyp isoform more easily induced by beta-naphtoflavone (βNF) in both Cx and Cll astrocytes, but oxidized bilirubin only after uncoupling by 3, 4,3',4'-tetrachlorobiphenyl (TCB). On the contrary, Cyp1A2 was the most active Cyp in bilirubin clearance without uncoupling, but its induction was confined only in Cx cells. Brain Cyp2A3 was not inducible. In conclusion, the exposure of astrocytes to βNF plus TCB significantly enhanced Cyp1A1 mediating bilirubin clearance, improving cell viability in both regions. These results may be a relevant groundwork for the manipulation of brain Cyps as a therapeutic approach in reducing bilirubin-induced neurological damage.

Gene replacement therapy for genetic hepatocellular jaundice.

Jaundice results from the systemic accumulation of bilirubin, the final product of the catabolism of haem. Inherited liver disorders of bilirubin metabolism and transport can result in reduced hepatic uptake, conjugation or biliary secretion of bilirubin. In patients with Rotor syndrome, bilirubin (re)uptake is impaired due to the deficiency of two basolateral/sinusoidal hepatocellular membrane proteins, organic anion-transporting polypeptide 1B1 (OATP1B1) and OATP1B3. Dubin-Johnson syndrome is caused by a defect in the ATP-dependent canalicular transporter, multidrug resistance-associated protein 2 (MRP2), which mediates the export of conjugated bilirubin into bile. Both disorders are benign and not progressive and are characterised by elevated serum levels of mainly conjugated bilirubin. Uridine diphospho-glucuronosyl transferase 1A1 (UGT1A1) is responsible for the glucuronidation of bilirubin; deficiency of this enzyme results in unconjugated hyperbilirubinaemia. Gilbert syndrome is the mild and benign form of inherited unconjugated hyperbilirubinaemia and is mostly caused by reduced promoter activity of the UGT1A1 gene. Crigler-Najjar syndrome is the severe inherited form of unconjugated hyperbilirubinaemia due to mutations in the UGT1A1 gene, which can cause kernicterus early in life and can be even lethal when left untreated. Due to major disadvantages of the current standard treatments for Crigler-Najjar syndrome, phototherapy and liver transplantation, new effective therapeutic strategies are under development. Here, we review the clinical features, pathophysiology and genetic background of these inherited disorders of bilirubin metabolism and transport. We also discuss the upcoming treatment option of viral gene therapy for genetic disorders such as Crigler-Najjar syndrome and the possible immunological consequences of this therapy.

Improved Efficacy and Reduced Toxicity by Ultrasound-Guided Intrahepatic Injections of Helper-Dependent Adenoviral Vector in Gunn Rats

Crigler-Najjar syndrome type I is caused by mutations of the uridine diphospho-glucuronosyl transferase 1A1 (UGT1A1) gene resulting in life-threatening increase of serum bilirubin. Life-long correction of hyperbilirubinemia was previously shown with intravenous injection of high doses of a helper-dependent adenoviral (HDAd) vector expressing UGT1A1 in the Gunn rat, the animal model of Crigler-Najjar syndrome. However, such high vector doses can activate an acute and potentially lethal inflammatory response with elevated serum interleukin-6 (IL-6). To overcome this obstacle, we investigated safety and efficacy of direct injections of low HDAd doses delivered directly into the liver parenchyma of Gunn rats. Direct hepatic injections performed by either laparotomy or ultrasound-guided percutaneous injections were compared with the same doses given by intravenous injections. A greater reduction of hyperbilirubinemia and increased conjugated bilirubin in bile were achieved with 1 × 10(11) vp/kg by direct liver injections compared with intravenous injections. In sharp contrast to intravenous injections, direct hepatic injections neither raised serum IL-6 nor resulted in thrombocytopenia. In conclusion, ultrasound-guided percutaneous injection of HDAd vectors into liver parenchyma resulted in improved hepatocyte transduction and reduced toxicity compared with systemic injections and is clinically attractive for liver-directed gene therapy of Crigler-Najjar syndrome.

Identifying term breast-fed infants at risk of significant hyperbilirubinemia

The aim of this study was to establish a model to identify term breast-fed infants who are at risk of developing significant neonatal hyperbilirubinemia. A prospective study was designed to investigate the effects of birth weight, mode of delivery, cephalohematoma, glucose-6-phosphate dehydrogenase (G6PD) deficiency, predischarge total serum bilirubin, variant uridine 5'diphospho-glucuronosyltransferase 1A1 (UGT1A1) gene, and hepatic solute carrier organic anion transporter 1B1 (SLCO1B1) gene on significant hyperbilirubinemia in term breast-fed neonates. Significant hyperbilirubinemia was defined as a bilirubin level exceeding the hour-specific phototherapy treatment threshold recommended by the American Academy of Pediatrics in 2004. Of 240 exclusively breast-fed term neonates, 26 (10.8%) had significant hyperbilirubinemia. The predischarge total serum bilirubin on the third day (odds ratio (OR) = 2.63; 95% confidence interval (CI): 1.87-3.70; P < 0.001) and the variant UGT1A1 gene at nucleotide 211 (OR = 5.00; 95% CI: 1.08-23.03; P < 0.05) were significant risk factors. The area under the receiver operating characteristic (ROC) curve of the predictive probability was 0.964 (95% CI: 0.932-0.984; P < 0.0001). Combining the total serum bilirubin on the third day and the variant UGT1A1 gene at nucleotide 211 can predict hyperbilirubinemia well in term breast-fed infants.

Effects of autophagy modulator on autophagy and uridine 5'-diphospho-glucuronosyltransferase 1A1 induced by sulforaphane

To explore the effects of 3-methyladenine (3-MA) and rapamycin (Rapa) on autophagy and uridine 5'-diphospho-glucuronosyltransferase 1A1 (UGT1A1) induced by sulforaphane (SFN) in human colon cancer Caco-2 cells. Western blot was used to detect the expression of microtubule-associated protein 1 light chain 3 (LC3) and UGT1A1 proteins. And immunocytochemistry was employed to observe the intracellular distribution of LC3 and nuclear localization of NF-E2-related factor 2 (Nrf2). Quantitative real-time reverse transcription-polymerase chain reaction (RT-PCR) was employed to examine the mRNA expression of UGT1A1 and human pregnane X receptor (hPXR). After the treatment of SFN, the LC3-II protein was induced in a dose and time-dependent manner. SFN-induced LC3-II protein could be attenuated and enhanced by 3-MA and Rapa respectively. In comparison with the control group, UGT1A1 mRNA levels increased significantly after the treatment of Rapa, SFN or their combination (2.4, 4.12 and 2.41 folds respectively, all P < 0.01). And the combination of SFN and Rapa possessed the highest level. UGT1A1 protein band intensity was also enhanced in three groups. There was no obvious nuclear staining of Nrf2 in control group while intense nuclear fluorescent labeling of Nrf2 could be observed in the SFN-treated groups, especially the combination group of SFN and Rapa. The hPXR mRNA levels increased significantly in the Rapa and combination groups (1.82 and 1.4 folds respectively, both P < 0.01). The treatment of 3-MA or Rapa may attenuate or enhance SFN-induced autophagy respectively. And Rapa also potentiates SFN-induced UGT1A1 expression. The mechanism for the synergic effect of Rapa and SFN on UGT1A1 induction may be a simultaneous activation of Nrf2 and hPXR signaling pathway.

Rescue of bilirubin‐induced neonatal lethality in a mouse model of Crigler‐Najjar syndrome type I by AAV9‐mediated gene transfer

Crigler-Najjar type I (CNI) syndrome is a recessively inherited disorder characterized by severe unconjugated hyperbilirubinemia caused by uridine diphosphoglucuronosyltransferase 1A1 (UGT1A1) deficiency. The disease is lethal due to bilirubin-induced neurological damage unless phototherapy is applied from birth. However, treatment becomes less effective during growth, and liver transplantation is required. To investigate the pathophysiology of the disease and therapeutic approaches in mice, we generated a mouse model by introducing a premature stop codon in the UGT1a1 gene, which results in an inactive enzyme. Homozygous mutant mice developed severe jaundice soon after birth and died within 11 d, showing significant cerebellar alterations. To rescue neonatal lethality, newborns were injected with a single dose of adeno-associated viral vector 9 (AAV9) expressing the human UGT1A1. Gene therapy treatment completely rescued all AAV-treated mutant mice, accompanied by lower plasma bilirubin levels and normal brain histology and motor coordination. Our mouse model of CNI reproduces genetic and phenotypic features of the human disease. We have shown, for the first time, the full recovery of the lethal effects of neonatal hyperbilirubinemia. We believe that, besides gene-addition-based therapies, our mice could represent a very useful model to develop and test novel technologies based on gene correction by homologous recombination.—Bortolussi, G., Zentilin, L., Baj, G., Giraudi, P., Bellarosa, C., Giacca, M., Tiribelli, C., Muro, A. F. Rescue of bilirubin-induced neonatal lethality in a mouse model of Crigler-Najjar syndrome type I by AAV9-mediated gene transfer.