Platycodon grandiflorus Polysaccharide Attenuates Inflammation by Inhibiting NLRP3 Inflammasome Activation via the ROS/NEK7 Pathway

Dysregulated activation of the NLRP3 inflammasome is a key driver in the pathogenesis of numerous inflammatory disorders. This study aimed to evaluate the protective effect of Platycodon grandiflorus polysaccharide (PGPSt) against NLRP3-inflammasome-mediated inflammation and elucidate its underlying mechanisms. An in vitro inflammatory model was established in porcine alveolar macrophages (3D4/21) using LPS/ATP co-stimulation. The effects of PGPSt were assessed by measuring inflammasome activation, intracellular reactive oxygen species (ROS) generation, and pro-inflammatory cytokine secretion. Molecular docking, alongside inhibitors (NAC, MCC950) and siRNA targeting NEK7, was employed to probe the involved mechanisms. PGPSt significantly suppressed NLRP3 inflammasome assembly and activation, reduced caspase-1 cleavage, and decreased the maturation and release of IL-1β and IL-18. It exerted its inhibitory effects through dual mechanisms: scavenging intracellular ROS and directly binding to NEK7 and NLRP3 to disrupt their interaction, as supported by molecular docking. The anti-inflammatory effect was diminished upon NEK7 knockdown. In conclusion, PGPSt is an effective natural inhibitor of the NLRP3 inflammasome, functioning through ROS clearance and direct interference with the NLRP3–NEK7 interaction. These findings propose PGPSt as a promising therapeutic candidate and further validate NEK7 as a potential target for treating NLRP3-driven inflammatory diseases.