Synthesis and pharmacological validation of fluorescent diarylsulfonylurea analogues as NLRP3 inhibitors and imaging probes

The NOD-like receptor family pyrin domain-containing protein 3 (NLRP3) is a key cytosolic pattern recognition receptor that senses diverse pathogen- and host-originated threat signals. Aberrant activation of NLRP3 inflammasomes is closely associated with the pathogenesis of various complex inflammatory diseases. Nevertheless, the detailed regulation mechanism of NLRP3 inflammasome and its pathogenic roles in the inflammation progression remain to be fully elucidated. Fluorescent imaging with small molecule probe can provide valuable visualization information on the expression, occupancy and bio-distribution of target protein. Herein, we reported a series of diarylsulfonylurea NLRP3 fluorescent inhibitors bearing an amino benzodiazole fluorophore. Compared to the previously reported NLRP3 fluorescent probes, these inhibitors are more structurally concise and membrane permeable due to no additionally appended fluorophore via a linker. Among this series, compound 13a exhibited the most potent cellular NLRP3 inhibitory effect with an IC₅₀ value of 49 nM, and significantly suppressed LPS/Nigericin-induced secretion of active caspase-1 and mature IL-1β in a dose-dependent manner to block the activation of NLRP3 inflammasome. Meanwhile, this new probe exhibited promising fluorescent properties for specifically detecting and imaging the LPS-induced or constitutively expressed NLRP3 proteins in RAW264.7 cells. Collectively, probe 13a is a potent NLRP3 fluorescent inhibitor with cellular NLRP3 imaging ability, which is useful for NLRP3 inhibitor screening and related mechanism study.