NLRP3 inflammasome may regulate inflammatory response of human periodontal ligament fibroblasts in an apoptosis‐associated speck‐like protein containing a CARD (ASC)‐dependent manner

Abstract Aim To explore the role of NLRP 3 ( NACHT [nucleotide‐binding oligomerization], LRR [leucine‐rich repeat] and PYD [pyrin domain] domains‐containing protein 3) inflammasome in the inflammatory response of human periodontal ligament fibroblasts ( HPDLF s). Methodology The expression of NLRP 3 and apoptosis‐associated speck‐like protein containing a CARD ( ASC ) in inflammatory periapical tissues and HPDLF s was examined by immunohistochemical and immunofluorescent staining. HPDLF s were stimulated with muramyl dipeptide ( MDP ) and lipopolysaccharide ( LPS ) from E. coli with or without the silencing of ASC . The expression of NLRP 3, ASC and caspase‐1 was examined using quantitative real‐time polymerase chain reaction. The secretion of proinflammatory cytokines, including interleukin‐1β ( IL ‐1β), interleukin‐6 ( IL ‐6) and tumour necrosis factor‐α ( TNF ‐α) was measured in the cell supernatant with an enzyme‐linked immunosorbent assay. Data were statistically analysed using independent sample t ‐tests. Results Immunohistochemistry and immunocytochemistry staining revealed that NLRP 3 and ASC were expressed in HPDLF s and inflammatory periapical tissues. MDP and LPS promoted the expression of NLRP 3, ASC and caspase‐1 in HPDLF s ( P < 0.05). The secretion of proinflammatory cytokines was also increased with MDP and LPS stimulation ( P < 0.05). After silencing ASC , the secretion of IL ‐1β induced by MDP and LPS was significantly attenuated ( P < 0.05). Conclusion In HPDLF s, MDP and LPS activated NLRP 3 inflammasome and induced IL ‐1β secretion. ASC plays an important role in this inflammatory response.