Endocannabinoids are associated with multiple regulatory functions in several tissues. The main endocannabinoids, anandamide (AEA) and 2-arachidonylglycerol (2-AG), have been detected in the gingival crevicular fluid of periodontitis patients, but the association between periodontal disease or human periodontal ligament cells (hPdLCs) and endocannabinoids still remain unclear. The aim of the present study was to examine the effects of AEA and 2-AG on the proliferation/viability and cytokine/chemokine production of hPdLCs in the presence/absence of Porphyromonas gingivalis lipopolysaccharide (P. gingivalis LPS). The proliferation/viability of hPdLCs was measured using 3,4,5-dimethylthiazol-2-yl-2,5- diphenyl tetrazolium bromide (MTT)-assay. Interleukin-6 (IL-6), interleukin-8 (IL-8), and monocyte chemotactic protein-1 (MCP-1) levels were examined at gene expression and protein level by real-time PCR and ELISA, respectively. AEA and 2-AG did not reveal any significant effects on proliferation/viability of hPdLCs in the absence of P. gingivalis LPS. However, hPdLCs viability was significantly increased by 10-20 mu M AEA in the presence of P. gingivalis LPS (1 mu g/ml). In the absence of P. gingivalis LPS, AEA and 2-AG did not exhibit any significant effect on the expression of IL-8 and MCP-1 expression in hPdLCs, whereas IL-6 expression was slightly enhanced by 10 mM 2-AG and not affected by AEA. In P. gingivalis LPS stimulated hPdLCs, 10 mu M AEA down-regulated gene-expression and protein production of IL-6, IL-8, and MCP-1. In contrast, 10 mu M 2AG had an opposite effect and induced a significant up-regulation of gene and protein expression of IL-6 and IL-8 (P<0.05) as well as gene-expression of MCP-1 in P. gingivalis LPS stimulated hPdLCs. Our data suggest that AEA appears to have an anti-inflammatory and immune suppressive effect on hPdLCs' host response to P. gingivalis LPS, whereas 2-AG appears to promote detrimental inflammatory processes. In conclusion, AEA and 2-AG might play an important role in the modulation of periodontal inflammation.