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

AIM: To explore the role of NLRP3 (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 (HPDLFs).

METHODOLOGY: The expression of NLRP3 and apoptosis-associated speck-like protein containing a CARD (ASC) in inflammatory periapical tissues and HPDLFs was examined by immunohistochemical and immunofluorescent staining. HPDLFs were stimulated with muramyl dipeptide (MDP) and lipopolysaccharide (LPS) from E. coli with or without the silencing of ASC. The expression of NLRP3, 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 NLRP3 and ASC were expressed in HPDLFs and inflammatory periapical tissues. MDP and LPS promoted the expression of NLRP3, ASC and caspase-1 in HPDLFs (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 HPDLFs, MDP and LPS activated NLRP3 inflammasome and induced IL-1β secretion. ASC plays an important role in this inflammatory response.