FAM20C restrains Caspase-1-dependent osteoblast pyroptosis in periodontal inflammation

FAM20C is elevated in inflamed periodontal tissues and LPS-treated cells. • Fam20c loss sensitizes osteoblasts to Caspase-1/GSDMD pyroptosis. • RNA-seq links Fam20c deficiency to pyroptosis and ER-stress signatures. • Metabolomics reveals purine and amino-acid metabolic remodelling. • Ac-YVAD-CMK reverses inflammatory activation in Fam20c-deficient cells. FAM20C is a secretory-pathway kinase required for mineralized-tissue homeostasis, and FAM20C-associated disease is accompanied by early periodontal inflammation. We investigated whether FAM20C limits Caspase-1-dependent osteoblast pyroptosis during periodontal inflammatory challenge. FAM20C/Fam20c expression was assessed by immunohistochemistry in ligature-induced mouse periodontitis and human gingiva and by RT-qPCR after lipopolysaccharide (LPS) exposure in four cell models. Stable Fam20c-deficient and Fam20c-overexpressing osteoblasts were analysed by transcriptomics, untargeted metabolomics, microscopy, immunofluorescence, RT-qPCR, Western blotting, ELISA and pharmacological Caspase-1 inhibition. FAM20C/Fam20c protein and mRNA increased in inflamed tissues, and LPS induced Fam20c expression. Fam20c deficiency increased ER-stress/Ca 2+ -homeostasis and inflammasome/pyroptosis module scores, reduced osteogenic gene expression and altered purine- and antioxidant-related metabolites. Fam20c loss enhanced LPS-induced cleaved Caspase-1, N-GSDMD and IL-1β/IL-18 release, whereas Fam20c overexpression attenuated these responses. Ac-YVAD-CMK reduced Caspase-1/GSDMD activation and cytokine release in Fam20c-deficient cells. These findings identify Fam20c as a determinant of osteoblast susceptibility to Caspase-1-dependent pyroptosis. Periodontal LPS induces an early FAM20C stress response. Genetic Fam20c deficiency disrupts ER/Ca 2+ and metabolic homeostasis, increases Caspase-1 activation and GSDMD cleavage, and amplifies osteoblast pyroptosis. Ac-YVAD-CMK reduces Caspase-1/GSDMD activation and cytokine release Download: Download high-res image (290KB) Download: Download full-size image