M2 Macrophages-Derived Exosomes Inhibited Podocyte Pyroptosis via lncRNA AFAP1-AS1/EZH2 Axis

Macrophage infiltration was closely associated with inflammatory injury of podocytes in diabetic nephropathy (DN), while how macrophages affected podocytes remained not entirely clear. Here, we not only investigated the relationship between macrophages and high glucose (HG)-treated podocytes, but the underlying mechanisms were also explored. Transmission electron microscopy, nanoparticle tracking analysis, and western blot of CD9, CD63, CD81, and Calnexin were performed to identify exosomes; QRT-PCR was performed to detect AFAP1-AS1 expression; Western blot was performed to examine NLRP3, Cleaved caspase-1, and GSDMD-N protein levels; Immunofluorescence was performed to assess co-localisation of NLRP3 and ASC; ELISA was performed to detect IL-18 and IL-1β levels; Cytotoxicity LDH Assay Kit was performed to detect LDH level; RNA pulldown was performed to determine the interaction of AFAP1-AS1 and EZH2; ChIP was employed to determine the interaction of EZH2 and H3K27me3 in the NLRP3 promoter region. The results showed that AFAP1-AS1 expression was down-regulated in the peripheral blood of DN patients, and exosomes derived from M2 macrophages transfected with si-AFAP1-AS1 enhanced HG-induced podocyte pyroptosis via significantly elevating NLRP3, Cleaved caspase-1, and GSDMD-N protein levels, immunofluorescence intensity of NLRP3 and ASC, as well as IL-18, IL-1β, and LDH levels. Mechanistically, AFAP1-AS1 interacted with EZH2 to transcriptionally regulate H3K27me3 level in the NLRP3 promoter region, thus epigenetically repressing NLRP3 level to inhibit podocyte pyroptosis. These results may provide an important target for improving kidney injury in DN.