Abstract
Introduction Inflammasomes are multiprotein complexes that regulate immune processes in response to infections and tissue damage. They modulate Interleukin-1beta (IL-1 beta) expression, a major proinflammatory cytokine. The inflammasome/IL-1 beta pathway is involved in head and neck squamous cell carcinoma (HNSCC) progression and the periodontal pathogensFusobacterium nucleatum(Fn) andPorphyromonas gingivalis(Pg) have been reported to cause chronic inflammation in HNSCC. The aim of this study was to characterise the role of these pathogens in regulating inflammasome activity and the IL-1 beta response in HNSCC in vitro. Methods An HNSCC cell line (H400) was exposed toFnandPgindividually or in combination for 24h, +/- incubation for 30 min with 5 mM adenosine triphosphate (ATP). Transcript levels of inflammasomes, NLRP3 and AIM2; inflammasome-regulatory proteins, POP1, CARD16 and TRIM16; and inflammasome-component, ASC and caspase 1 and IL-1 beta, were assayed by RT-PCR. Expression of IL-1 beta was by immunocytochemistry and ELISA. Results NLRP3 expression was significantly upregulated in response toPg,Fn + Pg,Pg + ATP andFn + Pg + ATP. AIM2 was significantly upregulated byFn,PgandFn + Pg + ATP exposure. All conditions significantly upregulated IL-1 beta gene expression. POP1 expression was significantly downregulated byPgorFnexposure but not byFn + Pg. Intracellular pro- and mature IL-1 beta were significantly higher followingFnandPg + ATP exposure. Conclusion Pgalone increased IL-1 beta by upregulating AIM2, NLRP3 and downregulating POP1.Fnpromoted IL-1 beta by increasing AIM2 and downregulating POP1.Pg + ATP with or withoutFnupregulated NLRP3, IL-1 beta by downregulating POP1. Periodontal pathogens may contribute to HNSCC pathogenesis by increasing the IL-1 beta response due to inflammasome dysregulation.