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Signal‐Regulated Protein Kinases/Protein Kinase B‐p53‐BH3–Interacting Domain Death Agonist Pathway Regulates Gingipain‐Induced Apoptosis in Osteoblasts
Author(s) -
Zhang Fuping,
Qiu Qihong,
Song Xiangchen,
Chen Yuting,
Wu Juan,
Liang Min
Publication year - 2017
Publication title -
journal of periodontology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.036
H-Index - 156
eISSN - 1943-3670
pISSN - 0022-3492
DOI - 10.1902/jop.2017.160806
Subject(s) - porphyromonas gingivalis , protein kinase b , mapk/erk pathway , kinase , chemistry , microbiology and biotechnology , apoptosis , small interfering rna , transfection , cancer research , biology , biochemistry , genetics , bacteria , gene
Background: Gingipains are cysteine proteases produced by Porphyromonas gingivalis , the predominant pathogen in chronic periodontitis. The present study aims to examine the role of gingipains in promoting apoptosis in osteoblasts. Methods: Human calvarial osteoblasts and osteoblast MC3T3‐E1 cells were treated with 8.348 U/L gingipains. Flow cytometry analysis and terminal deoxynucleotidyl transferase‐mediated deoxy‐UTP nick end labeling staining were used to detect cell apoptosis. Protein expression was examined by Western blotting, and gene expression was detected by real‐time polymerase chain reaction. Small interfering (si)RNA transfection was used to knock down BH3‐interacting domain death agonist (Bid) expression. Results: Treatment with 8.348 U/L gingipains from 4 to 72 hours increased apoptosis, accompanied by elevated cleaved caspase‐3 levels. Notably, gingipain‐induced apoptosis was associated with increase of Bid and its truncated form, tBid, as well as p53. Transfection with Bid siRNA resulted in suppression of gingipain‐induced apoptosis. The p53 inhibitor, Pifithrin‐α, blocked the gingipain‐induced Bid. The ability of gingipains to stimulate p53 and Bid expression was mimicked by PD‐0325901 and MK‐2206, the specific extracellular signal‐regulated protein kinases (ERK) and protein kinase B (PKB) inhibitors, respectively. Furthermore, treatment with gingipains reduced phospho‐ERK and phospho‐PKB levels, an effect correlated to gingipain‐induced increase in p53 and tBid expression. Conclusion: The present findings suggest that Bid plays an essential role in gingipain‐induced osteoblast apoptosis, which is dependent on inhibition of ERK and PKB phosphorylation, followed by the activation of p53.