Abstract Objectives This study sought to determine effects of Thai propolis extract mixed in mineral trioxide aggregate (MTA) on matrix metalloproteinase-2 (MMP-2) expression and its activity in inflamed human dental pulp cells (HDPCs). Materials and Methods Interleukin-1β-primed HDPCs were treated with either the eluate of MTA mixed with distilled water, of MTA mixed with 0.75 mg/ml of the propolis extract, or of Dycal®, 0.75 mg/ml of the propolis extract, or 0.2% (v/v) of chlorhexidine for 24 or 72 h. The viability of HDPCs was determined by the PrestoBlue® cytotoxic assay. HDPCs’ lysates were analyzed for MMP-2 mRNA expression by RT-qPCR, while their supernatants were measured for MMP-2 activity by gelatin zymography. Results At 24 and 72 h, a non-toxic dose of the propolis extract at 0.75 mg/ml by itself or mixed in MTA tended to reduce MMP-2 expression upregulated by MTA, while it further decreased the MMP-2 activity as compared to that of MTA mixed with distilled water. The MMP-2 activity of interleukin-1β-primed HDPCs treated with the eluate of the propolis extract mixed in MTA was significantly lower than that of interleukin-1β-primed HDPCs at 24 h (p=0.012). As a control, treatment with chlorhexidine significantly inhibited MMP-2 expression induced by MTA and MMP-2 activity enhanced by interleukin-1β (p<0.05). Treatment with Dycal® caused a significant increase in HDPC’s death, resulting in a significant decrease in MMP-2 expression and activity (p<0.05). Conclusions MTA mixed with Thai propolis extract can reduce MMP-2 mRNA expression and activity when compared to MTA mixed with distilled water in inflamed HDPCs. (MTA metalloproteinase2 metalloproteinase 2 metalloproteinase- MMP2 MMP (MMP-2 . (HDPCs) Interleukin1βprimed Interleukinβprimed Interleukin 1β primed β 075 0 75 0.7 mgml mg ml Dycal 02 0.2 v/v vv v (v/v 7 PrestoBlue assay MMP- RTqPCR, RTqPCR RT qPCR, qPCR RT-qPCR zymography nontoxic non toxic interleukin1βprimed interleukinβprimed interleukin p=0.012. p0012 p p=0.012 012 (p=0.012) control interleukin1β interleukinβ p<0.05. p005 p<0.05 05 (p<0.05) HDPC s death (MMP- (HDPCs βprimed 07 0. p001 p=0.01 01 (p=0.012 p00 p<0.0 (p<0.05 (MMP p=0.0 (p=0.01 p0 p<0. (p<0.0 p=0. (p=0.0 p<0 (p<0. p=0 (p=0. p< (p<0 p= (p=0 (p< (p= (p

Abstract Objective To explore the potential for development of Thai propolis extract as a pulp capping agent to suppress pulpal inflammation from dental pulp infections. This study aimed to examine the anti-inflammatory effect of the propolis extract on the arachidonic acid pathway, activated by interleukin (IL)-1β, in cultured human dental pulp cells. Methodology Dental pulp cells, isolated from three freshly extracted third molars, were first characterized for their mesenchymal origin and treated with 10 ng/ml of IL-1β in the presence or absence of non-toxic concentrations of the extract from 0.08 to 1.25 mg/ml, as determined by the PrestoBlue cytotoxic assay. Total RNA was harvested and analyzed for mRNA expressions of 5-lipoxygenase (5-LOX) and cyclooxygenase-2 (COX-2). Western blot hybridization was performed to investigate COX-2 protein expression. Culture supernatants were assayed for released prostaglandin E2 levels. Immunofluorescence was conducted to determine involvement of nuclear factor-kappaB (NF-kB) in the inhibitory effect of the extract. Results Stimulation of the pulp cells with IL-1β resulted in the activation of arachidonic acid metabolism via COX-2, but not 5-LOX. Incubation with various non-toxic concentrations of the propolis extract significantly inhibited upregulated COX-2 mRNA and protein expressions upon treatment with IL-1β (p<0.05), resulting in a significant decrease in elevated PGE2 levels (p<0.05). Nuclear translocation of the p50 and the p65 subunits of NF-kB upon treatment with IL-1β was also blocked by incubation with the extract. Conclusions Upregulated COX-2 expression and enhanced PGE2 synthesis upon treatment with IL-1β in human dental pulp cells were suppressed by incubation with non-toxic doses of Thai propolis extract via involvement of the NF-kB activation. This extract could be therapeutically used as a pulp capping material due to its anti-inflammatory properties. infections antiinflammatory anti inflammatory pathway IL1β, IL1β ILβ IL 1β, 1β β (IL)-1β molars 1 ngml ng ml nontoxic non toxic 008 0 08 0.0 125 25 1.2 mgml mg mg/ml assay 5lipoxygenase lipoxygenase 5 5LOX LOX (5-LOX cyclooxygenase2 cyclooxygenase 2 cyclooxygenase- COX2. COX2 COX . (COX-2) COX- E factorkappaB factor kappaB NFkB NF kB (NF-kB COX2, 2, 5LOX. LOX. 5-LOX p<0.05, p005 p p<0.05 , 05 (p<0.05) PGE p<0.05. p5 p6 properties 00 0. 12 1. (COX-2 p00 p<0.0 (p<0.05 (COX- p0 p<0. (p<0.0 (COX p<0 (p<0. p< (p<0 (p< (p