Cathepsin B/NLRP3/GSDMD axis-mediated macrophage pyroptosis induces inflammation and fibrosis in systemic sclerosis

Published:December 24, 2022DOI:


      • Macrophage pyroptosis was increased in SSc patients and BLM-induced SSc mouse model.
      • Inhibition of pyroptosis reduced inflammation and fibrosis of SSc mouse model.
      • Inhibiting NLRP3/GSDMD-mediated macrophage pyroptosis inactivates fibroblasts.



      Pyroptosis is a newly discovered type of programmed cell death associated with inflammatory and fibrotic diseases. Macrophages play an important role in inducing early immune inflammation in systemic sclerosis (SSc).


      To investigate the effect of macrophages pyroptosis on fibrosis of SSc.


      Pyroptosis/inflammatory markers in serum and skin of SSc patients were detected. Bleomycin (BLM) was subcutaneously injected to establish SSc mouse model. The levels of pyroptosis markers, dermal thickness and collagen deposition in skin were assessed before and after the administration of pyroptosis inhibitors, including MCC950, Disulfiram and necrosulfonamide (NSA). Human-derived monocyte-macrophage cell line (THP-1) or mouse bone marrow-derived macrophages (BMDMs) were primed with lipopolysaccharide (LPS) and stimulated by silicon dioxide (SiO2) to induce cell pyroptosis. Fibroblasts from patients with SSc were co-cultured with pyroptotic THP-1 cells, and the collagen production was assessed.


      Pyroptotic/inflammatory proteins, including NLRP3, cleaved-Caspase (CASP)1, GSDMD-N terminal and IL-18 were increased in the serum, and ASC aggregation and GSDMD were elevated in macrophages in the skin of SSc patients. SSc mice showed increased pyroptosis markers, dermal thickness and collagen deposition in skins, which were alleviated by MCC950, Disulfiram and NSA. Pyroptosis of THP-1 cells and BMDMs was induced by LPS/SiO2, and it was reduced by the inhibitors of Cathepsin B, NLRP3, CASP1 and GSDMD. Co-culture with pyroptotic THP-1 cells increased the fibrotic proteins in fibroblasts, which were alleviated by pyroptosis inhibitors.


      SSc patients and BLM-induced mouse model presented increased pyroptosis. LPS/SiO2-induced macrophage pyroptosis promoted fibrosis of SSc through Cathepsin B/NLRP3/GSDMD pathway.


      ASC (Apoptosis-associated speck-like protein containing a caspase recruitment domain), α-SMA (α-Smooth muscle actin), BLM (Bleomycin), BMDMs (Mouse bone marrow-derived macrophages), CASP1 (Caspase-1), DAPI (4′,6-diamidino-2-phenylindole), ELISA (Enzyme-linked immunosorbent assay), FBS (Fetal bovine serum), GSDMD (Gasdermin D), GSDMD-N (GSDMD N-terminal), HCs (Healthy controls), H&E (Hematoxylin and eosin), IL-1β (Interleukin-1β), IL-18 (Interleukin-18), LPS (Lipopolysaccharide), LDH (Lactate dehydrogenase), M-CSF (Macrophage colony-stimulating factor), NLRs (Nod-like receptors), NLRP3 (NLRs family pyrin domain containing 3), NSA (Necrosulfonamide), PMA (Phorbol 12-myristate 13-acetate), PI (Propidium iodide), SiO2 (Silicon dioxide), SSc (Systemic sclerosis), THP-1 (Human acute monocytic leukemia cell line)


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