Pharmacological Modulation of BMAL1 Alters Circadian Dynamics and the Macrophage Immune Response

The master transcription factor BMAL1-CLOCK is crucial for orchestrating rhythmic gene expression and governing circadian rhythms. Pharmacological manipulation of this central circadian regulator requires accessible protein cavities and selective compounds. By targeting BMAL1 through a resident cavity in its PAS-B domain, we demonstrate that the small-molecule Core Circadian Modulator (CCM) penetrates and substantially expands this pocket. Biochemical and cellular analyses validate CCM's target engagement selectivity, enabling direct access to BMAL1's transcriptional activities. CCM induces dose-dependent changes in PER2-Luc macrophage oscillations and selectively modifies expression patterns of circadian controlled genes. In activated macrophages, CCM modulates BMAL1-CLOCK controlled inflammatory and phagocytic pathways to promote their downregulation. Our findings demonstrate the feasibility of directly targeting BMAL1-CLOCK as a strategy for circadian regulation and targeting circadian-regulated processes Overall design: To investigate the specificity and effects of pharmacological manipulation of Bmal1, bone-marrow derived macrophages from both myeloid cell specific Bmal1-KO mice and littermate controls were treated with CCM. The effect of inflammation was monitored: this was done under both basal and stimulated conditions.