Propionate and butyrate attenuate macrophage pyroptosis and osteoclastogenesis induced by CoCrMo alloy particles

Background: Wear particles-induced osteolysis is a major long-term complication after total joint arthroplasty. Up to now, there is no effective treatment for wear particles-induced osteolysis except for the revision surgery, which is a heavy psychological and economic burden to patients. A metabolite of gut microbiota, short chain fatty acids(SCFAs),has been reported to be beneficial for many chronic inflammatory diseases. This study aimed to investigate the therapeutic effect of SCFAs on osteolysis.Methods: A model of inflammatory osteolysis was established by applying CoCrMo alloy particles to mouse calvarium.After two weeks of intervention, the anti-inflammatory effects of SCFAs on wear particle-induced osteolysis were evaluated by micro-CT analysis and immunohistochemistry staining. In vitro study, lipopolysaccharide(LPS) primed bone marrow-derived macrophages(BMDMs) and Tohoku hospital pediatrics-1(THP-1) macrophages were stimulated with CoCrMo particles to activate inflammasome in the presence of acetate(C2), propionate(C3), and butyrate(C4). Western blotting, enzyme-linked immunosorbent assay, and immunofluorescence were used to detect the activation of NLRP3 inflammasome. The effects of SCFAs on osteoclasts were evaluate by qRT-PCR, Western blotting,immunofluorescence, and tartrate-resistant acid phosphatase(TRAP) staining. Additionally, histone deacetylase(HDAC)inhibitors, agonists of GPR41, GPR43, and GPR109A were applied to confirm the underlying mechanism of SCFAs on the inflammasome activation of macrophages and osteoclastogenesis.Results: C3 and C4 but not C2 could alleviate wear particles-induced osteolysis with fewer bone erosion pits(P<0.001),higher level of bone volume to tissue volume(BV/TV, P<0.001), bone mineral density(BMD, P<0.001), and a lower total porosity(P<0.001). C3 and C4 prevented CoCrMo alloy particles-induced ASC speck formation and nucleationinduced oligomerization, suppressing the cleavage of caspase-1(P<0.05) and IL-1β(P<0.05) stimulated by CoCrMo alloy particles. C3 and C4 also inhibited the generation of gasdermin D-N-terminal fragment(GSDMD-NT) to regulate pyroptosis. Besides, C3 and C4 have a negative impact on osteoclast differentiation(P<0.05) and its function(P<0.05),affecting the podosome arrangement and morphologically normal podosome belts formation.Conclusions: Our work showed that C3 and C4 are qualified candidates for the treatment of wear particle-induced osteolysis.