A novel potential target of IL‐35‐regulated JAK/STAT signaling pathway in lupus nephritis

Abstract Background In this study, we have investigated the potential regulatory mechanisms of IL‐35 to relieve lupus nephritis (LN) through regulating Janus kinase (JAK)/signal transducers and activators of transcription (STAT) signaling pathway in mesangial cells. Results Among 105 significant differentially expressed proteins (DEPs) between juvenile systemic lupus erythematosus (JSLE) patients with LN and healthy controls, LAIR1, PDGFRβ, VTN, EPHB4, and EPHA4 were downregulated in JSLE‐LN. They consist of an interactive network with PTPN11 and FN1, which involved in IL‐35‐related JAK/STAT signaling pathway. Besides, urinary LAIR1 was significantly correlated with JSLE‐LN clinical parameters such as SLEDAI‐2K, %CD19+ B, and %CD3+ T cells. Through bioinformatics analysis of co‐immunoprecipitation with mass spectrometry results, including GO, KEGG, and STRING, five genes interacted with Lair1 were upregulated by IL‐35, but only Myh10 was downregulated. Therefore, we presumed an interactive network among these DEPs, JAK/STAT, and IL‐35. Moreover, the downregulated phosphorylated (p)‐STAT3, p‐p38 MAPK, and p‐ERK, and the upregulated p‐JAK2/p‐STAT1/4 in IL‐35 overexpressed mesangial cells, and RNA‐sequencing results validated the potential regulatory mechanisms of IL‐35 in alleviating JSLE‐LN disease. Moreover, the relieved histopathological features of nephritis including urine protein and leukocyte scores, a decreased %CD90+αSMA+ mesangial cells and pro‐inflammatory cytokines, the inactivated JAK/STAT signals and the significant upregulated Tregs in spleen, thymus and peripheral blood were validated in Tregs and IL‐35 overexpression plasmid‐treated lupus mice. Conclusions Our study provided a reference proteomic map of urinary biomarkers for JSLE‐LN and elucidated evidence that IL‐35 may regulate the interactive network of LAIR1‐PTPN11‐JAK‐STAT‐FN1 to affect JAK/STAT and MAPK signaling pathways to alleviate inflammation in JSLE‐LN. This finding may provide a further prospective mechanism for JSLE‐LN clinical treatment.