Effects of LPS and estrogen on PDL cell inflammatory response

Objectives: Several studies have addressed the association between changes in female sex hormone level and periodontitis. Information is lacking on the biological importance of estrogen in periodontal tissues. We have previously reported that PDL cells express preferentially estrogen receptor-b (ERb). The aim of this study was to investigate whether LPS induces the expression of cytokines and chemokines in PDL cells and to examine whether estrogen affects the LPS response. Another aim was to investigate the specificity of the LPS response by studying also functional characteristics of the cells.

Methods: The middle third of the periodontal ligament was scraped off from the root surface of teeth extracted for orthodontic reasons. The cells were cultured with LPS, with or without addition of physiological concentrations of estrogen for 1-21 days. The quantity of IL-6, CRP, MCP-1 and GROa protein was analyzed using ELISA. The mRNA for CXCL1 gene (coding for GROa) was analyzed using SYBR green Real-Time RT-PCR. Collagen and DNA synthesis was determined by incorporation of radiolabeled proline and thymidine, respectively.

Results: LPS induced PDL cell production of IL-6 and MCP-1 in a concentration and time dependent manner, CRP was not affected. LPS did not affect collagen and DNA synthesis. The potent PMN cell chemoattractant GROa was strongly induced by LPS. Preliminary data indicate that LPS induced GROa gene and protein is attenuated by estrogen.

Conclusions: Our data show that LPS enhances PDL cell production of MCP-1, IL-6 and GROa, but has no effect on normal cell characteristics, suggesting that the pro-inflammatory effect of LPS is specific. Preliminary data suggests that estrogen may have an anti-inflammatory via reduction of GROa.