Caveolin-1 serves as a negative effector in senescent human gingival fibroblasts during Fusobacterium nucleatum infection.

It is well established that aging is associated with increased susceptibility to infectious diseases. Fusobacterium nucleatum is a well-known bacterial species that plays a central bridging role between early and late colonizers in the human oral cavity. Further, the ability of F. nucleatum to invade gingival fibroblasts (GFs) is critical to the development of periodontal diseases. However, the mechanisms underlying the age-related infection of GFs by F. nucleatum remain unknown. We used young (fourth passage) and senescent (22nd passage) GFs to investigate the mechanisms of F. nucleatum infection in aged GFs and first observed increased invasion of F. nucleatum in senescent GFs. We also found that the co-localization of caveolin-1 (Cav-1), a protein marker of aging, with F. nucleatum and the knockdown of Cav-1 in GFs reduced F. nucleatum invasion. Additionally, F. nucleatum infection triggered the production of reactive oxygen species (ROS) through activation of NADPH oxidase in GFs, but senescent GFs exhibited significantly lower levels of NADPH oxidase activity and ROS production compared with young GFs in both the uninfected and infected conditions. Also, senescent GFs exhibited a decline in proinflammatory cytokine production and extracellular signal regulated kinase (ERK) phosphorylation following F. nucleatum infection. Interestingly, the knockdown of Cav-1 in senescent GFs increased NADPH oxidase activity and caused the upregulation of interleukin-6 and interleukin-8 and the phosphorylation of ERK. Collectively, the increased expression of Cav-1 might play a critical role in F. nucleatum invasion and could hinder the host response in senescent GFs.

Ahn SH ，Cho SH ，Song JE ，Kim S ，Oh SS ，Jung S ，Cho KA ，Lee TH ... -  《-》

NOX1/2 activation in human gingival fibroblasts by Fusobacterium nucleatum facilitates attachment of Porphyromonas gingivalis.

Ahn SH ，Song JE ，Kim S ，Cho SH ，Lim YK ，Kook JK ，Kook MS ，Lee TH ... -  《-》

Transcriptome profiling analysis of senescent gingival fibroblasts in response to Fusobacterium nucleatum infection.

Ahn SH ，Chun S ，Park C ，Lee JH ，Lee SW ，Lee TH ... -  《PLoS One》

Relatively low invasive capacity of Porphyromonas gingivalis strains into human gingival fibroblasts in vitro.

Bacterial invasion into host cells is a common strategy to escape the host immune system. Gingival fibroblasts (GFs) are the most predominant non-phagocytic cell type in gingival connective tissue. Therefore, invasion into GFs was thought to be the first strategy for the survival of Porphyromonas gingivalis. The present study compared the invasive ability of P. gingivalis into GFs with those of other red-complex and relatively less pathogenic bacterial strains, especially Fusobacterium nucleatum. Invasive ability of bacterial strains into GFs was measured using a flow cytometric invasion assay at a multiplicity of infection of 1000. The effect of dual infection with F. nucleatum CCUG 37843T on P. gingivalis ATCC 49417 invasion was investigated. The invasive ability of F. nucleatum and P. gingivalis was confirmed using confocal microscopy. The invasive ability of red-complex bacteria was markedly lower than that of F. nucleatum or Campylobacter gracilis. The invasive ability of 4 types and 10 clinical strains of P. gingivalis was less than 6%, and that of F. nucleatum strains was greater than 45%. Confocal analysis revealed that the percentage of bacteria invading GFs in the cell-treated P. gingivalis and F. nucleatum were 0.0068% and 1.22%, respectively. Dual infection with F. nucleatum increased the invasive ability of P. gingivalis. The invasive capacities of P. gingivalis into GFs were comparatively lower than those of relatively less pathogenic bacteria. Invasion into GFs cannot be the first strategy for survival of P. gingivalis in gingival connective tissue.

Jang JY ，Baek KJ ，Choi Y ，Ji S ... -  《-》

Fusobacterium nucleatum Facilitates Apoptosis, ROS Generation, and Inflammatory Cytokine Production by Activating AKT/MAPK and NF-κB Signaling Pathways in Human Gingival Fibroblasts.

Fusobacterium nucleatum (F. nucleatum) plays key roles in the initiation and progression of periodontitis. However, the pathogenic effect of F. nucleatum on human oral tissues and cells has not been fully evaluated. In this study, we aimed to analyze the pathogenic effects of F. nucleatum on human gingival fibroblasts (GFs) and clarify the potential mechanisms. RNA-sequencing analysis confirmed that F. nucleatum significantly altered the gene expression of GF as the stimulation time increased. Cell counting and EdU-labeling assays indicated that F. nucleatum inhibited GF proliferation and promoted cell apoptosis in a time- and dose-dependent manner. In addition, cell apoptosis, intracellular reactive oxygen species (ROS) generation, and proinflammatory cytokine production were dramatically elevated after F. nucleatum stimulation. Furthermore, we found that the AKT/MAPK and NF-κB signaling pathways were significantly activated by F. nucleatum infection and that a large number of genes related to cellular proliferation, apoptosis, ROS, and inflammatory cytokine production downstream of AKT/MAPK and NF-κB signaling pathways were significantly altered in F. nucleatum-stimulated GFs. These findings suggest that F. nucleatum inhibits GF proliferation and promotes cell apoptosis, ROS generation, and inflammatory cytokine production partly by activating the AKT/MAPK and NF-κB signaling pathways. Our study opens a new window for understanding the pathogenic effects of periodontal pathogens on the host oral system.

Kang W ，Jia Z ，Tang D ，Zhang Z ，Gao H ，He K ，Feng Q ... -  《-》