Abstract
Pregnane X receptor (PXR), a nuclear receptor known for modulating the transcription of drug metabolizing enzymes and transporters (DMETs), such as cytochrome P450 3A4 and P-glycoprotein, is functionally involved in chronic liver diseases of different etiologies. Furthermore, PXR activity relates to that of other NRs, such as constitutive androstane receptor (CAR), through a crosstalk that in turn orchestrates a complex network of responses. Thus, besides regulating DMETs, PXR signaling is involved in both liver damage progression and repair and in the neoplastic transition to hepatocellular carcinoma. We here summarize the present knowledge about PXR expression and function in chronic liver diseases characterized by different etiologies and clinical outcome, focusing on the molecular pathways involved in PXR activity. Although many molecular details of these finely tuned networks still need to be fully understood, we conclude that PXR and its modulation could represent a promising pharmacological target for the identification of novel therapeutical approaches to chronic liver diseases.
Highlights
This review summarizes the latest findings about Pregnane X receptor (PXR) expression and its role in the hepatic environment, focusing on its connection to chronic liver diseases of different etiologies and underlining the inconsistencies in the results that have sometimes been obtained by studies conducted with different approaches
Nonalcoholic fatty liver disease (NAFLD) comprises a variable degree of liver dysfunction ranging from simple steatosis, where lipid droplets accumulate within hepatocytes, to nonalcoholic steatohepatitis (NASH), characterized by hepatic inflammation and fibrosis [58,59]
It has been demonstrated that PXR activity is connected with that of other Nuclear receptors (NRs), such as constitutive androstane receptor (CAR)
Summary
The pregnane X receptor (PXR) belongs to the 1I subfamily and is a ligand-activated transcription factor, the classification of which is still controversial because a number of scientists still consider PXR an orphan receptor, many ligands have been notified, since it binds a variety of endogenous compounds and xenobiotics at high (micromolar) concentrations [4,5]. As for other NRs, the first event leading to PXR activation consists in the binding of the ligand to the receptor LBD [19]. This binding site, normally characterized by an “α-helical sandwich”, has a unique five-stranded β-sheet that acts as a homodimerization site, forming tryptophan-zipper interactions [1,18]. Biliary atresia showed a PXR downregulation in the late stage of obstructive cholestasis
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
