Porphyromonas gingivalis is a periopathogen strongly associated with the development of adult-type periodontitis. Both the virulence characteristics of periopathogens and host-related factors are believed to contribute to periodontitis. P. gingivalis lipopolysaccharide (LPS) displays a significant amount of lipid A structural heterogeneity, containing both penta-and tetra-acylated lipid A structures. However, little is known concerning how the lipid A structural content of P. gingivalis is regulated. Alterations in the lipid A content may facilitate the ability of P. gingivalis to modulate the innate host response to this bacterium. In this report, it is shown that the concentration of hemin in the growth medium significantly modulates the lipopolysaccharide lipid A structural content of P. gingivalis. Hemin is a key microenvironmental component of gingival cervicular fluid which is believed to vary depending upon the state of vascular ulceration. At low hemin concentrations, one major penta-acylated lipid A structure was found, whereas at high concentrations of hemin, multiple tetraand penta-acylated lipid A structures were observed. Hemin concentrations, not iron acquisition, were responsible for the alterations in the lipid A structural content. The modifications of the lipid A structural content were independent of the LPS extraction procedure and occurred in a variety of laboratory strains as well as a freshly obtained clinical isolate. The known hemin binding proteins Kgp and HmuR contributed to the lipid A modulation sensing mechanism. To the best of our knowledge, this is the first report that hemin, a clinically relevant microenvironmental component for P. gingivalis, can modulate the lipid A structure found in a bacterium. Since tetra-and penta-acylated P. gingivalis lipid A structures have opposing effects on Toll-like receptor 4 activation, the alteration of the lipid A structural content may have significant effects on the host response to this bacterium.Periodontitis is a chronic inflammatory disease of the tissue surrounding the tooth root surface. The disease is characterized by the loss of periodontal tissue and supporting alveolar bone. It is highly prevalent in the human population and is the major cause of tooth loss in the world (24). It is strongly associated with a subgingival microbial community (25) commonly referred to as periopathogenic dental plaque. Porphyromonas gingivalis, a gram-negative anaerobic bacterium, is a member of this community and displays a strong correlation with disease (25). Neither the contribution of periopathogenic plaque nor those of individual members of the periopathogenic community to the disease process are fully understood. However, it is suspected that both bacterial virulence factors, such as P. gingivalis protease secretion (17), and host factors contribute to the disease (18). The contribution of the host to the disease process is believed to result from an innate host response to periopathogenic bacteria that results in tissue damage and alveolar bone ...

SummaryPorphyromonas gingivalis is a Gram-negative bacterium strongly associated with periodontitis, a chronic inflammatory disease of the tissue surrounding the tooth root surface. Lipopolysaccharide (LPS) obtained from P. gingivalis is unusual in that it has been shown to display an unusual amount of lipid A heterogeneity containing both tetra-and penta-acylated lipid A structures. In this report, it is shown that penta-acylated lipid A structures facilitate E-selectin expression whereas tetra-acylated lipid A structures do not. Furthermore, it is shown that tetra-acylated lipid A structures are potent antagonists for E-selectin expression. Both tetra-and penta-acylated lipid A structures interact with TLR4 although experiments utilizing human, mouse and human/mouse chimeric TLR4 proteins demonstrated that they interact differentially with the TLR4 signalling complexes. The presence of two different structural types of lipid A in P. gingivalis LPS, with opposing effects on the Eselectin response suggests that this organism is able to modulate innate host responses by alterations in the relative amount of these lipid A structures.

We previously demonstrated that high external [Ca(2+)] activated two Ca(2+) currents in human gingival keratinocytes (HGKs): an initial small I(CRAC)-like current and a second large nonspecific cation current (Fatherazi S, Belton CM, Cai S, Zarif S, Goodwin PC, Lamont RJ, Izutsu KT; Pflugers Arch 448:93-104, 2004). It was recently shown that TRPC1, a member of the transient receptor potential protein family, is a component of the store-operated calcium entry mechanism in keratinocytes. To further elucidate the molecular identity of these channels, we investigated the expression of TRPC4 in gingival tissue and in cultured keratinocytes, and the effect of knockdown of TRPC4 expression on the Ca(2+) currents and influx. Immunohistochemistry showed TRPC4 was present in gingival epithelium as well as in HGKs cultured in different [Ca(2+)]s. Results from tissue and cultured HGKs demonstrated TRPC4 expression decreased with differentiation. Knockdown of TRPC4 in proliferating HGKs with antisense oligonucleotides significantly reduced the intracellular [Ca(2+)] increase obtained upon exposure to high external [Ca(2+)]. Antisense knockdown of TRPC4 expression was confirmed by reverse transcriptase polymerase chain reaction, Western blot, and immunofluorescence microscopy of transfected HGKs. Immunofluorescence microscopy and patch clamp measurements in Lucifer-yellow-tagged, antisense-treated HGKs showed attenuation of TRPC4 expression levels as well as attenuation of the I(CRAC)-like current in the same cell, whereas the large nonspecific cation current was unchanged but significantly delayed. Cells transfected with a scrambled TRPC4 oligonucleotide showed no change in either the I(CRAC)-like or nonspecific currents. The results indicate that TRPC4 is an important component of the I(CRAC)-like channel in HGKs.

Aim:The null hypothesis is that there is no difference in the post-operative antiinflammatory efficacy of chlorhexidine (CHX), 2% saline rinses (SR) and a herbal mouthwash (MW) after non-surgical mechanical debridement (MD) for treatment of peri-implant mucositis (PiM). The aim was to compare the post-operative antiinflammatory efficacy of CHX, 2% SR and a herbal oral rinse after non-surgical MD of PiM. Materials and Methods:The present randomized controlled trial had a single-blinded parallel arm design. Patients diagnosed with PiM were enrolled. Demographic information was recorded. All patients underwent MD and were randomly divided into 4 groups: CHX-group: 0.12% non-alcoholic CHX; Sodium chloride (NaCl) group: 2% NaCl rinses; Herbal MW group: Herbal-based MW and H 2 O group: distilled water with peppermint flavour. After MD, all the participants were advised to rinse twice daily (every 12 hrs) for 2 weeks with their respective MWs. In all groups, peri-implant modified plaque index (mPI), modified gingival index (mGI) and probing depth (PD) were measured at baseline and at 12 weeks of follow-up. Sample size was estimated using data from a pilot investigation; and group-comparisons were performed. Statistical significance was confirmed when P-values were below 0.01.Results: Sixty individuals (15 patients/group) were included. At baseline, mPI, mGI and PD were comparable in all groups. At baseline, there was no significant difference in peri-implant mPI, mGI and PD in all groups. At 12-weeks' follow-up, there was a statistically significant reduction in peri-implant mPI (p < 0.01), mGI (p < 0.01) and PD (p < 0.01) in CHX, NaCl and herbal MW groups compared with H 2 O group. There was no significant relation between implant location, duration for which, implants were functional, gender and peri-implant clinical parameters in all groups. Conclusion:After non-surgical MD, post-operative use of CHX and herbal and NaCl MWs is useful for the management of PiM in the short-term.