More than microglial depletion: PLX5622 activates the hepatic constitutive androstane receptor to alter anesthesia and addiction.

The colony-stimulating factor 1 receptor (CSF1R) inhibitor PLX5622 has been widely used to deplete microglia for functional characterization and therapeutic support. Although diverse outcomes have been described after PLX5622 treatment, whether these phenotypes solely reflect microglial functions remains to be determined. Here, we show that transgenic microglial depletion did not mimic the accelerated anesthetic arousal or the alleviated nicotine addiction withdrawal symptoms observed after PLX5622 treatment in mice. We further identify that PLX5622 potently activates the mouse constitutive androstane receptor (CAR), leading to prominent induction of hepatic enzymes. The induced enzymatic activity enhances the metabolism and clearance of anesthetics and nicotine, thereby contributing to anesthetic insensitivity and addiction relief. Inactivation of CAR abolished these effects of PLX5622, indicating that the impact of PLX5622 treatment cannot be attributed exclusively to microglial depletion. Our findings raise awareness in evaluating consequences of PLX5622 treatment and provide insights into the design of specific CSF1R inhibitors.