[Effect of exogenous ATP on NLRP3 inflammasome activation in gingival fibroblasts cells].

PURPOSE: To investigate exogenous ATP-dependent activation of NLRP3 inflammasome and interleukin-1ß ( IL-1ß) secretion in P.gingivalis infected and heat-killed P.gingivalis induced gingival fibroblasts cells ( hGFs) in vitro. METHODS: Gingival tissues were obtained from healthy patients and hGFs were cultured in vitro with tissue block method to harvest primary cells. HGFs was simulated by being treated with 100 MOI live P.gingivalis or 100 MOI heat-killed P.gingivalis (HP.gingivalis) after 5 mmol/L ATP pre-treatment. Real-time PCR was carried out to assess mRNA expression of NLRP3, ASC, caspase-1 and IL-1ß. The protein level of NLRP3 , caspase-1 and IL-1ß was evaluated by Western blot. IL-1ß secretion was measured using ELISA. Statistical analysis was performed using Graphpad prism 6 statistical package and the measurement data were analyzed by t test or one-way ANOVA. RESULTS: Compared with the control group, P.gingivalis downregulated NLRP3 mRNA and ASC mRNA while upregulated IL-1ß mRNA. Moreover, the protein expression of NLRP3 and IL-1ß was decreased. The gene and protein expression of NLRP3, ASC and IL-1ß was induced by HP.gingivalis, while caspase-1mRNA and IL-1ßsecretion was free from P.gingivalis or HP.gingivalis stimulus. All those genes as well as intracellular protein expression and IL-1ßsecretion were significantly potentiated with ATP/P.gingivalis or ATP/HP.gingivalis stimuli in hGFs. CONCLUSIONS: Exogenous ATP may be a potential stimulus signal in favour of NLRP3 inflammasome activation of hGFs and mediated inflammatory factor IL-1ß secretion.

[Expression of a DNA fragment encoding the active domain of human TNF related apoptosis inducing ligand in pichia pastoris].

Human tumor necrosis factor-related apoptosis-inducing ligand(TRAIL) is a member of the tumor necrosis factor (TNF) family of ligands which has been reported in 1995. The TRAIL protein induces apoptosis of certain types of target cells, such as transformed cells that include but are not limited to cancer cells and virus-infected cells but the normal cells. It is a type II transmembrane protein and the extracellular domain of TRAIL is the functional domain in induction of cell apoptosis. A gene fragment encoding for the active domain of TRAIL was modified with oligo-nucleotide directed mutagenesis according to the characters of Pichia pastoris expressing vector. Arginine at the position of 149 corresponding to the amino acid residue 531 which might be a potential Kex2 protease processing sites was substituted with Lysine to prevent the expressed protein from the digestion by the protease. After proved with DNA sequencing. the modified gene fragment coding soluble TRAIL domain was inserted into the Pichia pastoris expression vector pPIC9K in the same reading frame with alpha-factor secreting signal peptide. The recombinant plasmid pPIC9K - TRAIL was transferred into P. pastoris cell by spheroplast transformation. The recombinant yeasts were identified by antibiotic G418 and Southern dot blot. The transformants (His+ Mut(s)) containing multi-copy gene fragment of TRAIL were selected with increasing concentration of G418 and induced with 0.5% methanol in shaking flask to expression the active domain of TRAIL. After inducing for 3 - 4 days, the proteins in the culture supernatant was assayed with SDS-PAGE and Western blot. Two expressed protein bands whose appearant molecular weight were 19kD and 38kD, respectively, could be specifically recognized by polyclonal antibodies against human TRAIL. The 38kD protein might be a dimers of TRAIL in the culture supernatant. The amount of expressed foreign protein made up to 36% of the total proteins in the culture suprenatant. Biological activity assay, in vitro, indicated that the expressed protein could induce tumor cells apoptosis.