Studies have revealed the role of inflammation in the onset, progression and pathogenesis of gingivitis and periodontitis. Nigella sativa
(NS) is known for its anti-inflammatory activities. This study therefore investigated the role of NS methanol extract and its bioactive component, thymoquinone (TQ) on gingival inflammation in Porphyromonas gingivalis
.LPS)-stimulated human gingival fibroblasts (HGFs). HGFs in culture were stimulated with P.g
.LPS (100 ng/mL) following pre-treatment with NS (12.5, 25 and 50 μg/mL) or TQ (2.5, 5 and 10 μM). Levels of NO., PGE2
, IL-1β, IL-6, IL-8 and TNF-α production were measured from culture supernatants by ELISA. Protein levels of COX-2, iNOS, phosphorylated-p38, Nrf2, HO-1 and NQO-1 were determined by western blot. Phosphorylation of NF-κB-p65 sub-unit protein expression was determined by In-cell western and ELISA. Phosphorylated-IκB-α, total-IκB, phosphorylated-ERK1/2, phosphorylated-JNK1/2, pro-and active-MMP-9 from extracts were also determined by ELISA. HGFs were transfected with Promega pGL4.32[luc2P/NF-κB-RE/Hygro] vector and reporter gene assays were employed to explore the effect of NS on NF-κB luciferase activity in the nucleus. NS methanol extract blocked the production of NO., PGE2
, IL-6 and TNF-α in P.g.
LPS-stimulated HGFs. Protein levels of phosphorylated-NF-κB-p65 sub-unit as well as phosphorylated-IκB-α were significantly suppressed by NS while an elevation in total-IκB protein level was observed. NF-κB binding as well as its transactivational activities were markedly inhibited by NS in P.g
.LPS-stimulated HGFs. TQ significantly inhibited the production of IL-1β, IL-6, IL-8 and TNF-α. COX-2 and iNOS mediated production of PGE2and NO. respectively were significantly blocked by TQ in P.g
.LPS-stimulated HGFs. Increases in P.g
.LPS-mediated phosphorylation of ERK1/2, p38 and JNK1/2 MAPKs was significantly blocked by TQ. Pro-MMP-9 protein as well as the secretion of active enzyme was also significantly suppressed by TQ in P.g
.LPS-stimulated HGFs. Protein levels of Nrf2, HO-1 and NQO-1 were significantly elevated by TQ in HGFs. These results suggest that N Sand TQ suppressed gingival inflammation through mechanisms involving NF-κB and MAPK and activation of antioxidant defense mechanisms. This study also demonstrates that bioactive TQ and NS are potential adjunctive therapeutic candidates in the prevention and treatment of gingivitis.