Impact of Aggregatibacter actinomycetemcomitans on inflammasome regulation and epigenetic changes in grade C periodontitis

Objectives: The NLRP3 inflammasome amplifies inflammation and may contribute to the destruction of tooth-supporting tissues in periodontitis. This study evaluated the expression of inflammasome markers (NLRP3, AIM2, IL-1β, TNF-α, CASP1, IL-10, TLR2, and TLR4) and the epigenetic patterns of NLRP3 and IL-1β in primary gingival fibroblasts from healthy individuals and patients with Grade C periodontitis (PerioC). Materials and methods: Cells were exposed to Aggregatibacter actinomycetemcomitans Protein Extract (AaPE) (5 µg/ml) for 1.5 h. After the experimental period, total RNA and DNA were collected and extracted. Total RNA was isolated and gene expressions of TLR2, TLR4, NLRP3, CASP1, AIM2, IL-10, IL-1β and TNF-α were analyzed via qPCR. DNA methylation and hydroxymethylation patterns of the IL-1β and NLRP3 genes were evaluated. Statistical analyses were performed considering a significance level of 5%. Results: Fibroblasts from PerioC exhibited higher AIM2 levels before and after stimulation compared to healthy individuals (p < 0.05). Conversely, IL-10 expression was lower in PerioC before AaPE incubation (p < 0.05). NLRP3 expression increased post-stimulation in healthy cells but remained unchanged in PerioC. IL-1β expression was consistently lower in PerioC in both conditions. The NLRP3 gene showed reduced methylation after AaPE exposure only in healthy fibroblasts, resulting in lower methylation levels compared to PerioC (p < 0.05). Conclusions: PerioC fibroblasts exhibited dysregulated inflammasome-related gene expression and a distinct epigenetic response to AaPE, suggesting altered local immune regulation at the transcriptional level. Clinical relevance: Patients with severe and rapidly progressing periodontitis exhibit an altered inflammasome-related gene expression and epigenetic response to bacterial stimulation. The reduced transcriptional responsiveness of inflammatory mediators and distinct DNA methylation profile observed in PerioC cells may contribute to ineffective host defense and persistent periodontal tissue destruction.