title: Porphyromonas gingivalis induce apoptosis in human gingival epithelial cells through a gingipain-dependent mechanism.
abstract: BACKGROUND
  The oral pathogen Porphyromonas gingivalis has been shown to modulate apoptosis in different cell types, but its effect on epithelial cells remains unclear.
  
  
  RESULTS
  We demonstrate that primary human gingival epithelial cells (HGECs) challenged with live P. gingivalis for 24 hours exhibit apoptosis, and we characterize this by M30 epitope detection, caspase-3 activity, DNA fragmentation and Annexin-V staining. Live bacteria strongly upregulated intrinsic and extrinsic apoptotic pathways. Pro-apoptotic molecules such as caspase-3, -8, -9, Bid and Bax were upregulated after 24 hours. The anti-apoptotic Bcl-2 was also upregulated, but this was not sufficient to ensure cell survival. The main P. gingivalis proteases arginine and lysine gingipains are necessary and sufficient to induce host cell apoptosis. Thus, live P. gingivalis can invoke gingival epithelial cell apoptosis in a time and dose dependent manner with significant apoptosis occurring between 12 and 24 hours of challenge via a gingipain-dependent mechanism.
  
  
  CONCLUSIONS
  The present study provides evidence that live, but not heat-killed, P. gingivalis can induce apoptosis after 24 hours of challenge in primary human gingival epithelial cells. Either arginine or lysine gingipains are necessary and sufficient factors in P. gingivalis elicited apoptosis.
authors.affiliation: Center for Oral Health and Systemic Disease, School of Dentistry, University of Louisville, Louisville, KY, USA. p0stat01@gwise.louisville.edu
authors.forename: Panagiota G
authors.initials: PG
authors.lastname: Stathopoulou
authors.forename: Johnah C
authors.initials: JC
authors.lastname: Galicia
authors.forename: Manjunatha R
authors.initials: MR
authors.lastname: Benakanakere
authors.forename: Carlos A
authors.initials: CA
authors.lastname: Garcia
authors.forename: Jan
authors.initials: J
authors.lastname: Potempa
authors.forename: Denis F
authors.initials: DF
authors.lastname: Kinane
mesh_terms: D018829:Adhesins, Bacterial / Q000378:metabolism*; D017209:Apoptosis; D053148:Caspase 3 / Q000378:metabolism; D002478:Cells, Cultured; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D053938:DNA Fragmentation; D004847:Epithelial Cells / Q000382:microbiology / Q000473:pathology*; D020869:Gene Expression Profiling; D000080867:Gingipain Cysteine Endopeptidases; D005881:Gingiva / Q000166:cytology* / Q000382:microbiology; D006801:Humans; D016966:Porphyromonas gingivalis / Q000201:enzymology*
chemical_list: D018829:Adhesins, Bacterial; D000080867:Gingipain Cysteine Endopeptidases; D053148:Caspase 3; D003546:Cysteine Endopeptidases