The UDP-glucuronosyltransferase (UGT) 2B enzymes are important in the detoxification of a variety of endogenous and exogenous compounds including many hormones, drugs and carcinogens. Identifying novel mechanisms governing their expression is important in understanding patient-specific response to drugs and cancer risk factors. In silico prediction algorithm programs were utilized to screen for microRNAs (miRNA) as potential regulators of UGT2B enzymes with miR-216b identified as a potential candidate. Luciferase data suggested the presence of a functional miR-216b binding motif within the 3' untranslated regions of UGTs 2B7, 2B4 and 2B10. Over-expression of miR-216b mimic significantly repressed UGT2B7 (P<0.001) and UGT2B10 (P=0.0018) mRNA levels in HuH-7 cells, and UGT2B4 (P<0.001) and UGT2B10 (P=0.018) mRNA in Hep3B cells. UGT2B7 protein levels were repressed in both HuH-7 and Hep3B cells in the presence of increasing miR-216b concentrations, corresponding with significant (P<0.001 and P=0.011, respectively) decreases in glucuronidation activity against the UGT2B7-specific substrate, epirubicin. Inhibition of endogenous miR-216b levels significantly increased UGT2B7 mRNA levels in HuH-7 (P=0.0205) and Hep3B (P=0.0068) cells, and increased epirubicin glucuronidation by 85% (P=0.057) and 50% (P=0.012) for HuH-7 and Hep3B cells, respectively. UGT2B4 activity against codeine and UGT2B10 activity against nicotine were significantly decreased in both HuH-7 and Hep3B cells (P<0.001 and P=0.0048, and P=0.017 and P=0.043, respectively) after over-expression of miR-216b mimic. This is the first evidence that miRNAs regulate UGTs 2B7, 2B4 and 2B10 expression and that miR-216b regulation of UGT2B proteins may be important in regulating the metabolism of UGT2B substrates.
- The American Society for Pharmacology and Experimental Therapeutics