4-Methylumbelliferyl glucuronide contributes to hyaluronan synthesis inhibition

Abstract

Edited by Peter Cresswell 4-Methylumbelliferone (4-MU) inhibits hyaluronan (HA) synthesis and is an approved drug used for managing biliary spasm. However, rapid and efficient glucuronidation is thought to limit its utility for systemically inhibiting HA synthesis. In particular, 4-MU in mice has a short half-life, causing most of the drug to be present as the metabolite 4-methylumbelliferyl glucuronide (4-MUG), which makes it remarkable that 4-MU is effective at all. We report here that 4-MUG contributes to HA synthesis inhibition. We observed that oral administration of 4-MUG to mice inhibits HA synthesis, promotes FoxP3 ؉ regulatory T-cell expansion, and prevents autoimmune diabetes. Mice fed either 4-MUG or 4-MU had equivalent 4-MU:4-MUG ratios in serum, liver, and pancreas, indicating that 4-MU and 4-MUG reach an equilibrium in these tissues. LC-tandem MS experiments revealed that 4-MUG is hydrolyzed to 4-MU in serum, thereby greatly increasing the effective bioavailability of 4-MU. Moreover, using intravital 2-photon microscopy, we found that 4-MUG (a nonfluorescent molecule) undergoes conversion into 4-MU (a fluorescent molecule) and that 4-MU is extensively tissue bound in the liver, fat, muscle, and pancreas of treated mice. 4-MUG also suppressed HA synthesis independently of its conversion into 4-MU and without depletion of the HA precursor UDP-glucuronic acid (GlcUA). Together, these results indicate that 4-MUG both directly and indirectly inhibits HA synthesis and that the effective bioavailability of 4-MU is higher than previously thought. These findings greatly alter the experimental and therapeutic possibilities for HA synthesis inhibition.

Characteristics of Hyaluronan Synthesis Inhibition by 4-Methylumbelliferone in Orbital Fibroblasts

“…Another doubt is the low bioavailability and short half-life of 4-MU; in a recent study its main metabolite 4-MUG was found to contribute to the bioactivity of 4-MU both in vitro and in vivo via conversion to 4-MU. 42 This conversion was observed in cell cultures after 48-72 hours 42 ; this may explain why the 24-hour 4-MUG treatment in our study was not sufficient to exert any effect on OFs and DFs.…”

Balance Between Tooth Size and Tooth Number Is Controlled by Hyaluronan

“…In this work, we considered that the effects of 4-Mu are due to the inhibition of HA-synthesis. 4-Mu is a highly specific inhibitor, and it is unlikely to affect any key pathways other than HA synthesis ( Nakamura et al, 1995 ; Kakizaki et al, 2004 ; Kultti et al, 2009 ; Nagy et al, 2019 ). However, we cannot excluded the possibility that 4-Mu might be affecting other targets that control the sequential formation of molars.…”

Cell Energy Metabolism and Hyaluronan Synthesis

“…4-MU is a fluorescent derivative of coumarin widely used in experimental conditions to specifically inhibit HA production both in vitro and in vivo models. 31,79-82 Although the mechanism of action is still under debate, some evidences demonstrated that 4-MU is metabolized to 4-MU-glucuronide (4-MUG) functioning as a competitive substrate for UDP-glucuronosyltransferase (UGT) with the consequent decline of UDP-GlcUA concentration and HA levels. 83 Other mechanisms proposed are based on HAS2 and HAS3 inhibition, 83 as well on UPP and dehydrogenase (UGDH) mRNA reduction.…”