Maackiain, a compound derived from Sophora flavescens, increases IL‐1β production by amplifying nigericin‐mediated inflammasome activation

Sophora flavescens is used as a traditional herbal medicine to modulate inflammatory responses. However, little is known about the impact of (‐)‐maackiain, a compound derived from S. flavescens, on the activation of inflammasome/caspase‐1, a key factor in interleukin‐1β (IL‐1β) processing. Here, we report that (‐)‐maackiain potently amplified caspase‐1 cleavage in macrophages in response to nigericin (Nig). In macrophages primed with either lipopolysaccharide or monophosphoryl lipid A, Nig‐mediated caspase‐1 cleavage was also markedly promoted by (‐)‐maackiain. Notably, (‐)‐maackiain induced the production of vimentin, an essential mediator for the activation of the NOD‐, LRR‐, and pyrin domain‐containing protein 3 inflammasome, thereby contributing to promotion of the formation of the inflammasome complex to activate caspase‐1. Taken together, our data suggest that (‐)‐maackiain exerts an immunostimulatory effect by promoting IL‐1β production via activation of the inflammasome/caspase‐1 pathway. Thus, the potent inflammasome‐activating effect of (‐)‐maackiain may be clinically useful as an acute immune‐stimulating agent.