Honokiol suppresses the aberrant interactions between renal resident macrophages and tubular epithelial cells in lupus nephritis through the NLRP3/IL-33/ST2 axis

Lupus nephritis (LN) is a type of immune-complex nephritis caused by systemic lupus erythematosus and is a major contributor to mortality and morbidity. Honokiol (HNK) has been found to have a therapeutic effect on LN, but its action mechanism remains unclear. In this study, we first demonstrated that HNK attenuates kidney injury in MRL/lpr mice. Results from RNA sequencing combined with ingenuity pathway analysis suggested that HNK plays an anti-LN role through inhibition of the NLRP3 inflammasome and IL33. GEO chip data, single-cell data, and clinical samples from LN patients demonstrated that the pyroptosis and IL-33/ST2 pathways are abnormally activated during the stage of LN. In vivo, similar to the results of the AAV-mediated NLRP3 shRNA MRL/lpr model, HNK downregulated serum and renal IL-33 levels, and suppressed NLRP3 inflammasome and the IL-33/ST2 axis in the kidney. In vitro, co-culturing NLRP3-overexpressing or IL-33 knocked-down rat renal macrophages with NRK-52E cells confirmed that NLRP3 activation in resident macrophages directly upregulates IL-33, which in turn mediates the IL-33/ST2/NF-κB pathway to promote the inflammatory response of renal tubular epithelial cells. Furthermore, a molecular docking model and surface plasmon resonance analysis were utilized to demonstrate a direct interaction between HNK and NLRP3. In conclusion, this study provides a novel anti-LN treatment strategy in which HNK plays a preventive and therapeutic role against LN by suppressing the abnormal crosstalk between renal resident macrophages and renal tubular epithelial cells by inhibiting the activation of the NLRP3/IL-33/ST2 axis.