[Effects and mechanisms of Egr-1 on inflammatory responses induced by mechanical stress in human periodontal ligament cells].

PURPOSE: To investigate the effects and mechanisms of silencing Egr-1 on MS-mediated secretion and expression of inflammatory cytokines in hPDLs. METHODS: The secretion and expression of IL-1β, IL-6, IL-8 and IL-11 were detected using ELISA and RT-PCR when cells were cultured with or without various duration (6, 12, 24 and 48 h) and force (3%, 6%, 12%, 15%) of mechanica stress (MS). RT-PCR and Western blotting were used to evaluate the expression of Egr-1 under a 12% MS for 24 h. The roles of silencing Egr-1 in MS-mediated expression of inflammatory cytokines were determined using ELISA and RT-PCR. The protein levels of PTEN/PI3K/Akt signaling pathway were determined using Western blotting. Moreover, cells were pretreated with 20 μmol/L LY294002 for 30 min, in order to study the mechanisms of Egr-1 in MS-mediated secretion and expression of inflammatory cytokines. Statistical analysis was performed using SPSS 11.0 software package. RESULTS: The secretion and expression of IL-1β, IL-6, IL-8 and IL-11 were increased gradually with the time under a MS force of 12% in hPDLs, and peaked in cells after exposure to MS for 24 h. The mRNA and protein levels of Egr-1 were elevated in hPDLs after exposure to 12% MS for 24 h. Moreover, depletion of Egr-1 inhibited MS-mediated secretion and expression of inflammatory cytokines. Knockdown of Egr-1 reduced the protein level of PTEN, and increased the protein expression of p-PI3K and p-Akt in hPDLs. LY294002 blocked partially the inhibitory roles of Egr-1 in the secretion and expression of inflammatory cytokines. CONCLUSIONS: Depletion of Egr-1 suppressed the secretion and expression of inflammatory cytokines induced by MS through PTEN/PI3K/Akt pathway.