Primary Human Macrophages Exhibit Functional CYP3A4 Activity with Marked Expression-Function Discordance and Cocaine-Induced Catalytic Activation

CYP3A4 is a phase I drug-metabolizing enzyme responsible for transformation of ∼50% of clinically relevant drugs. While extensively characterized in hepatocytes, its role in immune cells remains poorly understood. Here, using primary human monocyte-derived macrophages, we identify an understudied extrahepatic site of CYP3A4-mediated drug metabolism. Macrophages from 100 independent donors expressed CYP3A4 and its transcriptional regulators, Pregnane X Receptor (PXR) and Constitutive Androstane Receptor (CAR), with substantial interindividual variability. Importantly, CYP3A4 protein expression was accompanied by measurable catalytic activity in intact macrophages, yet CYP3A4 mRNA, protein abundance, and activity lacked concordance, demonstrating that expression alone may not predict function. In vivo , CYP3A4 was expressed in rhesus macaque Kupffer cells, further supporting macrophages as a potential pharmacologic entity. We next evaluated cocaine as a potential modulator of CYP3A4, due to its role in xenobiotic clearance. Cocaine had a dichotomous effect on expression, increasing CYP3A4 in some donors while producing no change or decreases in others, a phenotype associated with PXR, CAR, and the sigma-1 cocaine receptor. Strikingly, despite these divergent expression responses, cocaine increased CYP3A4 catalytic activity in all donors, reaching or exceeding levels induced by rifampicin, a clinically relevant CYP3A4 inducer. In rhesus macaques, cocaine also decreased antiretroviral therapy tissue concentrations, coincident with increased CYP3A4 and PXR. Together, these findings establish macrophages as a functionally active extrahepatic site of CYP3A4 metabolism and reveal a critical disconnect between CYP3A4 expression and catalytic function. Moreover, our findings identify interindividual variability and expression-activity discordance as important considerations for personalized medicine and understanding clinically relevant drug-drug interactions in the context of substance use.

CYP3A4 is best known for its role in hepatic drug metabolism, but its function in other cell types remains poorly understood. This work establishes macrophages as a functionally active extrahepatic site of CYP3A4-mediated drug metabolism, with marked interindividual variability and poor concordance between CYP3A4 expression and activity. Cocaine-enhanced CYP3A4 activity, together with altered antiretroviral tissue disposition in vivo , supports macrophage drug metabolism as a potential contributor to variability in therapeutic responses and substance use-associated drug-drug interactions.