Yang Xiao

The activation of stimulator of interferon genes (STING) and NOD-like receptor protein 3 (NLRP3) inflammasome-mediated pyroptosis signaling pathways represent two distinct central mechanisms in liver disease. However, the interconnections between these two pathways and the epigenetic regulation of the STING-NLRP3 axis in hepatocyte pyroptosis during liver fibrosis remain unknown. STING and NLRP3 inflammasome signaling pathways are activated in fibrotic livers but are suppressed by Sting knockout. Sting knockout ameliorated hepatic pyroptosis, inflammation, and fibrosis. In vitro, STING induces pyroptosis in primary murine hepatocytes by activating the NLRP3 inflammasome. H3K4-specific histone methyltransferase WD repeat-containing protein 5 (WDR5) and DOT1-like histone H3K79 methyltransferase (DOT1L) are identified to regulate NLRP3 expression in STING-overexpressing AML12 hepatocytes. WDR5/DOT1L-mediated histone methylation enhances interferon regulatory transcription factor 3 (IRF3) binding to the Nlrp3 promoter and promotes STING-induced Nlrp3 transcription in hepatocytes. Moreover, hepatocyte-specific Nlrp3 deletion and downstream Gasdermin D (Gsdmd) knockout attenuate hepatic pyroptosis, inflammation, and fibrosis. RNA-sequencing and metabolomics analysis in murine livers and primary hepatocytes show that oxidative stress and metabolic reprogramming might participate in NLRP3-mediated hepatocyte pyroptosis and liver fibrosis. The STING-NLRP3-GSDMD axis inhibition suppresses hepatic ROS generation. In conclusion, this study describes a novel epigenetic mechanism by which the STING-WDR5/DOT1L/IRF3-NLRP3 signaling pathway enhances hepatocyte pyroptosis and hepatic inflammation in liver fibrosis.

BACKGROUND: Alpha-kinase 1 (ALPK1) is a master regulator in inflammation and has been proved to promote renal fibrosis by promoting the production of IL-1β in diabetic nephropathy (DN) mice. Pyroptosis is involved in high glucose (HG)-induced tubular cells injury, characterized by activation of Gasdermin D (GSDMD) and the release of IL-1β and IL-18, resulting in inflammatory injury in DN. It is reasonable to assume that ALPK1 is involved in pyroptosis-related tubular injury in DN. However, the mechanism remains poorly defined. METHODS: Immunohistochemistry (IHC) staining was performed to detect the expression of pyroptosis- and fibrosis-related proteins in renal sections of DN patients and DN mice. DN models were induced through injection of streptozotocin combined with a high-fat diet. Protein levels of ALPK1, NF-κB, Caspase-1, GSDMD, IL-1β, IL-18 and α-SMA were detected by Western blot. HK-2 cells treated with high-glucose (HG) served as an in vitro model. ALPK1 small interfering RNA (siRNA) was transfected into HK-2 cells to down-regulate ALPK1. The pyroptosis rates were determined by flow cytometry. The concentrations of IL-1β and IL-18 were evaluated by ELISA kits. Immunofluorescence staining was used to observe translocation of NF-κB and GSDMD. RESULTS: macrophages were positively correlated with tubular injury in DN patients. Western blot analysis showed increased expressions of ALPK1, phospho-NF-κB P65, GSDMD-NT, and IL-1β in renal tissues of DN mice and HK-2 cells, accompanied with increased renal fibrosis-related proteins (FN, α-SMA) and macrophages infiltration in interstitial areas. Inhibition of ALPK1 attenuated HG-induced upregulation expressions of NF-κB, pyroptosis-related proteins Caspase-1, GSDMD-NT, IL-1β, IL-18, α-SMA, and pyroptosis level in HK-2 cells. Also, the intensity and nuclear translocation of NF-κB and membranous translocation of GSDMD were ameliorated in HG-treated HK-2 cells after treatment with ALPK1 siRNA. CONCLUSIONS: Our data suggest that ALPK1/NF-κB pathway initiated canonical caspase-1-GSDMD pyroptosis pathway, resulting in tubular injury and interstitial inflammation of DN.

Abstract Supported single‐atom catalysts (SACs) are promising in heterogeneous catalysis because of their atom economy, unusual transformations, and mechanistic clarity. The metal SAs loading, however, limits the catalytic efficiency. Herein, an in situ pre‐metallated monomer‐based preparation strategy is shown to achieve ultrahigh Au SAs loading in catalyst formations. The polymerization of single‐atom loaded monomers yield a new porous aromatic framework (PAF‐164) with Au SAs loading up to a record high 45.3 wt.%. SACs of Au‐PAFs exhibit excellent photocatalytic activity in hydrogen (H 2 ) evolution, and the H 2 evolution rate of Au 100% ‐SAs‐PAF‐164 can reach 4.82 mmol g −1 h −1 with great recyclability.