Activatable Proximity-Labeled Fluorogenic Probe for Visualizing the Role of Estrogen in Regulating Liver Carboxylesterase Expression

Estradiol (E2), the most potent form of estrogen, holds a central position in regulating physiological functions and influencing disease states across the female lifecycle. Carboxylesterases (CEs), as a widely distributed drug-metabolizing enzyme in human liver and plasma, play a crucial role in the hydrolytic metabolism of drugs, and their activities are significantly affected by estrogen levels, making the interplay between E2 and CEs particularly important. Thus, elucidating how E2 modulates CEs is vital for refining drug therapy, particularly for pregnant and postmenopausal women. In this study, we presented a proximity-labeled fluorogenic probe DCI2F-MC. This probe reacted with CEs, producing a quinone methide (QM) intermediate bound to the enzyme's active site and emitting fluorescence signals, enabling highly selective detection and in situ imaging of CEs activity. DCI2F-MC exhibited superior <i>in vitro</i> spectral response properties and facilitated the screening of cell lines based on variations in CEs levels. Additional experiments revealed that E2 decreased the CEs expression in LO2 cells in a dose-dependent manner, potentially through transcriptional regulation or the AP-1 pathway. Most importantly, in an ovariectomized mouse model, E2 supplementation markedly reduced CEs activity in the liver, the finding confirmed by <i>in vivo</i> fluorescence imaging and Western blot analysis. Our results provided chemical tools for understanding the mechanisms of estrogen regulation of CEs and offered a scientific basis for personalized drug therapy in women under different physiological conditions.