Determination of mRNA Expression of Human UDP-Glucuronosyltransferases and Application for Localization in Various Human Tissues by Real-Time Reverse Transcriptase-Polymerase Chain Reaction

Abstract

ABSTRACT:An exhaustive real-time reverse transcriptase-polymerase chain reaction (PCR) quantification method was used to determine 15 of the catalytically active human UDP-glucuronosyltransferase (UGT) isoforms (1A1, 1A3, 1A4, 1A5, 1A6, 1A7, 1A8, 1A9, 1A10, 2B4, 2B7, 2B10, 2B11, 2B15, and 2B17). The specific primers for respective human UGTs were developed for differential determination. The cDNA derived from the 1A7 isoform was detected in the esophagus, the 1A8 and 1A10 isoforms were detected in the small intestine, and all other isoforms were detected in at least the liver by PCR. In all cases, single bands of the expected size on the agarose gel were confirmed to correspond with the predicted UGT isoform sequences. Each calibration curve showed linearity between the PCR crossing point and the calibrator copy number. The correlation coefficients were greater than 0.9957 with high reproducibility. This exhaustive measurement method was applied to UGT expression in 23 human tissue types. UGT was mostly expressed in the alimentary system and liver. We were surprised to find that extremely high expression in the liver was found for UGT2B4 and UGT2B15, which had, respectively, 8.98 and 4.38 times greater expression than UGT2B7 in the liver. In addition, even though expressed at low levels, several UGT isoforms were expressed in steroidogenic tissues, such as the breast, prostate, heart, and adrenal. Therefore, this quantification method may provide valuable information about the medical efficacy or pharmacokinetic characteristics of a wide variety of UGT-metabolized drugs.

Quantitative profiling of the UGT transcriptome in human drug-metabolizing tissues

“…17 Still, expression data are consistent with lower expression of UGTs in kidney and colon tissues as previously reported using other approaches, at the mRNA and protein levels. [18][19][20][21][22] Our preliminary observations also suggest a shift in the transcript profiles in kidney and intestine/colon tumors that requires additional investigations using a larger set of well-characterized tumor samples.…”

Characterization of UDP-Glucuronosyltransferases Involved in Glucuronidation of Diethylstilbestrol in Human Liver and Intestine

“…The lack of the UGTs results in that DES can not be timely detoxicated via glucuronidation and therefore freely exerts the severe damage in the reproductive system. Unlike the reproductive tract, UGT1A1, -1A3, and -2B7 are abundant in the liver, 17 in which DES can be effectively glucuronidated, and thereby displays fewer damages. This can explain, at least partly, why injury of DES prefers the reproductive systems other than liver, despite the fact that both of these two tissues are DES accumulation sites.…”

“…All UGTs with DES glucuronidation activity were not detected in the reproductive system including ovary, cervix, and testes. 17 In fact, in these tissues, only UGT1A7, -2B15, and -2B17 are expressed; 17 nevertheless, these UGTs can not catalyze DES glucuronidation. The lack of the UGTs results in that DES can not be timely detoxicated via glucuronidation and therefore freely exerts the severe damage in the reproductive system.…”

“…16 As compared with the liver, there are a very limited number of uridine 5′-diphospho-glucuronosyltransferase (UGTs) expressed in the reproductive tract. 17 Similarly, the fetus possesses a relatively very low glucuronidation activity in comparison with adults. 18 It appears to be that the lack of UGTs with DES glucuronidation activity in the genital tract and the low glucuronidation activity in the fetus may contribute to the tissue preference of damage in offspring of DES.…”

“…19 They are expressed in various tissues in a tissue-dependent manner. 17 Each isoform displays different substrate preferences, despite usually exhibiting overlapping substrate specificities. 20 Many factors, such as polymorphism, age, and coadministrated compounds, can influence the activities of UGTs, which are often in isoformdependent manners.…”