Cathelicidin (LL‐37) causes expression of inflammatory factors in coronary artery endothelial cells of Kawasaki disease by activating TLR4–NF‐κB–NLRP3 signaling

Abstract Background Kawasaki disease (KD) is a type of vasculitis with an unidentified etiology. Cathelicidin (LL‐37) may be involved in the development of the KD process; therefore, further research to investigate the molecular mechanism of LL‐37 involvement in KD is warranted. Methods Enzyme‐linked immunosorbent assay (ELISA) was used to detect the levels of tumor necrosis factor‐α (TNF‐α), interleukin (IL)‐1β, NLRP3, and LL‐37 in the sera of healthy subjects, children with KD, and children with pneumonia. Subsequently, human recombinant LL‐37 or/and toll‐like receptors 4 (TLR4)‐specific inhibitor TAK‐242 stimulated human coronary artery endothelial cells (HCAECs), CCK‐8 was used to detect cell proliferation, flow cytometry to detect apoptosis, transmission electron microscopy to observe cytoskeletal changes, Transwell to measure cell migration ability, ELISA to detect inflammatory factor levels, Western blot analysis to analyze protein levels of toll‐like receptors 4 (TLR4) and NF‐κB p‐65, and quantitative real‐time polymerase chain reaction (qRT‐PCR) to determine LL‐37, NLRP3 mRNA levels. Results In this study, we found that the level of LL‐37 was highly expressed in the serum of children with KD, and after LL‐37 stimulation, apoptosis was significantly increased in HCAECs, and the expression levels of TLR4, NLRP3 and inflammatory factors in cells were significantly enhanced. Intervention with the TLR4‐specific inhibitor TAK‐242 significantly alleviated the LL‐37 effects on cellular inflammation, TLR4, NLRP3 promotion effect. Conclusions Our data suggest that LL‐37 induces an inflammatory response in KD coronary endothelial cells via TLR4‐NF‐κB‐NLRP3, providing a potential target for the treatment of KD.