Umbilical cord mesenchymal stromal cells-derived HGF inhibits STING-mediated pyroptosis to alleviate cerebral ischemia/reperfusion injury via c-Met/β-catenin/RNF5 pathway

Pyroptosis plays an essential role in the pathological process of cerebral ischemia/reperfusion (I/R) injury. Hepatocyte growth factor (HGF)-modified stem cells improve brain I/R damage. This research investigated whether umbilical cord mesenchymal stromal cells (UCMSCs)-derived HGF affected pyroptosis post brain I/R injury. Rats were subjected to middle cerebral artery occlusion (MCAO), and neurons (H19-7 or HT-22) were exposed to oxygen-glucose deprivation/reperfusion (OGD/R), to establish cerebral I/R injury models in vivo and in vitro. Exosomes were isolated from UCMSCs, before added into cells. Brain injury was assessed by triphenyltetrazolium chloride (TTC) staining, modified neurological severity score (mNSS), and hematoxylin and eosin staining. Cell viability and pyroptosis were assessed using cell counting kit-8 (CCK-8) and flow cytometry, respectively. Inflammatory cytokines interleukin (IL)-18 and IL-1β were detected with enzyme-linked immunosorbent assay (ELISA). Protein expressions were measured by western blot and immunohistochemistry. The interactions between molecules were determined using co-immunoprecipitation, chromatin immunoprecipitation, and dual-luciferase assay. Ring finger protein 5 (RNF5) was downregulated, and stimulator of interferon gene (STING) was activated in MCAO rats and OGD/R-exposed cells. RNF5 mediated ubiquitination and degradation of STING. RNF5 overexpression inhibited STING-mediated pyroptosis in OGD/R-treated cells. UCMSCs-exosomes suppressed pyroptosis, which was reversed when silencing HGF in UCMSCs-exosomes or adding with cellular mesenchymal-epithelial transition factor (c-Met) inhibitor. The effects of HGF-silenced UCMSCs-exosomes were overturned by activating c-Met. β-catenin recruited T-cell factor 4 (TCF4) to promote RNF5 transcription. HGF-overexpressed UCMSCs-exosomes repressed pyroptosis, which was counteracted by RNF5 knockdown. UCMSCs-derived exosomal HGF attenuated cerebral I/R injury through inhibiting STING-mediated pyroptosis via c-Met/β-catenin/RNF5 pathway. Our study provided a promising therapeutic strategy for brain I/R damage.