P. gingivalis initially suppresses but later promotes osteoblast apoptosis. A. Western blot demonstrating the initial weak (day 1–7) but later more intense (day 14–21) cleaved caspase-3 expression in P. gingivalis-infected osteoblasts compared with uninfected control cells. Actin is the loading control. B. Quantitative densitometric analysis of cleaved caspase-3 by western blotting. Abbreviations: Ctrl, non-infected osteoblasts; PG, P. gingivalis infected osteoblasts; D, day. C. TUNEL assay showing significantly less apoptotic osteoblasts from day 1–7, followed by significantly more apoptotic osteoblasts from day 14–21 in P. gingivalis-infected cultures compared with uninfected control cells. Arrows denote condensed, blue-stained, apoptotic osteoblast nuclei. Nuclease treatment and exclusion of TdT enzyme were used as positive and negative controls, respectively. D. Quantitative analysis of the TUNEL assay data. Abbreviations: (+) Ctrl, nuclease treated, used as positive technique control; (-) Ctrl, exclusion of TdT enzyme, used as negative technique control; CT, uninfected osteoblasts; PG, P. gingivalis infected osteoblasts; D, day. Scale bar = 20 μm. * denotes P < 0.05.
Zhang et al. BMC Microbiology 2013 13:5 doi:10.1186/1471-2180-13-5