The protective role of curcumin in human dental pulp stem cells stimulated by lipopolysaccharide via inhibiting NF-κB p65 phosphorylation to suppress NLRP3 inflammasome activation

Objectives This study aims to investigate the anti-inflammatory effect of curcumin and underlying mechanisms regarding the modulation of the nod-like receptor pyrin domain containing 3 (NLRP3) inflammasome in human dental pulp stem cells (hDPSCs). Materials and methods The impact of curcumin on the viability of hDPSCs was evaluated. The effect of curcumin on the expression of IL-1β and NLRP3 in hDPSCs stimulated by lipopolysaccharide (LPS) was assessed. Then, LPS-primed hDPSCs were pre-treated with curcumin before ATP triggering NLRP3 inflammasome activation, and NLRP3 inflammasome-related mediators were assessed. The mechanism of curcumin inactivation of LPS plus ATP-induced inflammasome associated with NF-κB pathway was explored. The NF-κB pathway related pro-inflammatory mediators at mRNA and protein levels were evaluated. The expression of NF-κB p65 and phosphorylation p65 was visualized after curcumin or NF-κB inhibitor administrating respectively in hDPSCs with an activated NLRP3 inflammasome. Statistical analysis was performed. Results While curcumin at the concentration of 0.5–5 μM showed no obvious impact on the viability of hDPSCs, it significantly decreased IL-1β and NLRP3 mRNA expression in LPS-induced hDPSCs in a dose-dependent manner. Curcumin significantly inhibited the LPS plus ATP-primed NLRP3 inflammasome activation in hDPSCs (NLRP3, ASC, caspase-1, and IL-1β). Curcumin evidently attenuated the LPS plus ATP-induced expression of NF-κB pathway-related pro-inflammatory mediators (IL-6, IL-8, TNF-α, and COX-2). Furthermore, curcumin effectively reduced p65 phosphorylation, which acts as an NF-κB inhibitor in hDPSCs with an activated NLRP3 inflammasome. Conclusions Curcumin pre-treatment may exert an anti-inflammatory role via inactivation of the NLRP3 inflammasome by inhibiting NF-κB p65 phosphorylation in cultured hDPSCs. Clinical relevance Curcumin may have therapeutic potential in pulp inflammation.