No abstract

The oral mucosa is exposed to a high density and diversity of gram-positive and gram-negative bacteria, but very little is known about how immune homeostasis is maintained in this environment, particularly in the inflammatory disease chronic periodontitis (

The available evidence suggested that submucosal debridement with adjunctive local delivery of antibiotics, submucosal glycine powder air polishing, or Er:YAG laser treatment may reduce clinical signs of peri-implant mucosal inflammation to a greater extent relative to submucosal debridement using curettes with adjunctive irrigation with chlorhexidine. Long-term randomized controlled trials are needed to assess the efficacy of non-surgical therapy on progressing bone loss, implant survival rates, and measures of oral health-related quality of life.

Transmission of HIV-1 through the oral cavity is considered to be a rare event. To identify factors in resistance/susceptibility to oral HIV-1 infection, we analyzed expression in human gingiva of HIV-1 receptors Langerin, DC-SIGN, MR, and GalCer, HIV-1 co-receptors CCCR5, CXCR4, and anti-microbial protein alpha-defensin-1. Our results show that healthy gingiva is infiltrated with cells expressing all HIV-1 receptors tested; however, there are very few CCR5(+) cells and a complete absence of CXCR4(+) cells in the lamina propria. In chronic periodontitis (CP), DC-SIGN, MR, CXCR4, and CCR5 increase, but this was accompanied by a ten-fold increase in alpha-defensin-1 mRNA. The CCR5(+) cells were revealed to be T-cells, macrophages, and dermal dendritic cells. Moreover, epithelial expression of GalCer and CXCR4 together was not apical and showed no trend with underlying inflammation. Thus, low expression of HIV-1 co-receptors in health and high expression of alpha-defensin during CP may comprise endogenous factors that provide protection from oral HIV-1 infection.

Our group and others have shown in vitro that repeated exposure of human mononuclear cells (MNC) to lipopolysaccharide can induce endotoxin tolerance, evidenced by downregulation of TLR2 and TLR4 mRNA and surface protein; moreover, the ability of the MNC to secrete inflammatory cytokines is reduced. In situ studies performed on diseased and healthy gingiva suggest that a similar pattern of endotoxin tolerance occurs in human oral mucosa with chronic periodontitis (CP). We hypothesized that this represents a fundamental immunoregulatory mechanism to restore immune homeostasis and protect the host from further tissue damage. In the current study, we extend these published studies by providing evidence that Src homology 2 containing inositol phosphatase, an inhibitor of NF-B activation and a negative regulator of the immune response, is upregulated in the oral mucosa during CP compared to its level during gingival health. We have also isolated MNC from patients with CP and those with healthy gingiva and show that MNC from CP subjects have a reduced capacity to upregulate TLR2, TLR4, and interleukin-1␤ in response to endotoxin. Thus, we provide more definitive evidence for a basic mechanism of immunoregulation in the oral mucosa.The ability to discriminate harmful microbes from commensal species is probably the most important property of the mucosal immune system, essential for maintaining a healthy host. Mucosal diseases, where the host inappropriately responds to commensal gut flora and to food antigens, are exemplified by Crohn's disease (1) and celiac disease (12), respectively. The Toll-like receptors (TLRs) are pattern recognition receptors that can rapidly identify microbial structures (e.g., peptidoglycan and lipopolysaccharide [LPS]) (2, 26, 30) and provoke an appropriate adaptive immune response (19). Chronic exposure to microbial structures such as LPS can lead to a selective and a transient hyporesponsive state called endotoxin tolerance. Antigen-presenting cells made tolerant ("tolerized") in this manner have a reduced capacity to initiate an adaptive immune response (7,8,29). The molecular mechanisms involved in endotoxin tolerance are still unclear but include downregulation of TLRs (17,20), alterations in signaling events downstream of Toll-like receptor (TLR) signaling (7, 16), and the induction of immune regulatory molecules such as Src homology 2 (SH2)-containing inositol phosphatase (SHIP), an inhibitor of NF-B signaling (14,23,24).Chronic periodontitis (CP) is an inflammatory disease of the oral mucosa (22) mediated by exposure to dental plaque, which contains Ͼ500 taxa of oral bacteria, ϳ60% of which are cultivable (15, 21). Nonetheless, the disease appears to be associated with a small subset of species that share the common property of being gram negative, i.e., producing LPS (4, 9, 25). Our published results suggest that the host may respond to the products of these gram-negative species by downregulation of TLR2 and TLR4 at the level of transcription (17). This observation was corroborated ...

The innate and the adaptive arms of the mucosal immune system must be coordinated to facilitate the control of pathogenic invasion while maintaining immune homeostasis. Toll-like receptors, able to activate the cell to produce bactericidal and inflammatory cytokines but also able to upregulate antigen (Ag)-presenting and costimulatory molecules, are particularly important in this regard. We have previously shown that the chronically infected oral mucosa is in a state of endotoxin tolerance, as evidenced by the downregulation of Toll-like receptors 2 and 4 and of inflammatory cytokines and the upregulation of SH2-containing inositol phosphatase, an inhibitor of NF-B signaling. In the present study, we hypothesized that endotoxin tolerance would influence the ability of human macrophages to engage in Ag capture and killing of the oral pathogen Porphyromonas gingivalis and to upregulate costimulatory molecules and stimulate autologous T-cell proliferation. We show that uptake, but not killing, of P. gingivalis 381 is enhanced by endotoxin tolerance. Reduced killing is possibly due to a reduction of the intracellular lysosomes. We further show that the expression of the Ag-presenting molecule HLA-DR and costimulatory molecules CD40 and CD86 is dampened by endotoxin tolerance to the constitutive level. This, along with our previous evidence for reduction in immunostimulatory cytokines, is consistent with the observed decrease in the induction of autologous CD4؉ T-cell proliferation by endotoxin-tolerized macrophages. Overall, these studies suggest that endotoxin tolerance, as observed in the inflamed oral mucosa, potentiates the innate Ag capture activity of macrophages but diminishes the potential of human macrophages to initiate the adaptive immune response. In conclusion, endotoxin tolerance, while helpful in bacterial clearance and in surmounting excessive inflammatory tissue damage, could potentially reduce the (protective) adaptive immune response during chronic infections such as periodontitis.Coordination of the innate and the adaptive arms of the immune response is required for the efficient and effective elimination of infectious agents (1, 46). The Toll-like receptors (TLRs) of the innate immune system recognize distinct microbial signatures known as pathogen-associated molecular patterns and marshal an immediate response in order to destroy the invading pathogens, including the induction of inflammatory cytokines and nitric oxide (41) and the release of reactive oxygen species (34). Moreover, TLR-mediated signaling leads to phagosome maturation in antigen (Ag)-presenting cells (APCs) (3) through the formation and fusion of lysosomes to facilitate the efficient loading of processed antigenic peptides on major histocompatibility complex (MHC) class II molecules. Furthermore, the transcription and secretion of immunostimulatory cytokines (29, 40) and of chemokines (45) and the expression of costimulatory molecules such as CD40, CD86, and CD80 (3, 13) are initiated by TLR ligation. These events all help to el...

Combined treatment of BMP2 and doxycycline in PDL cells counteracts the osteogenic mediators. Molecular interaction of growth factors should be explored before using a combination of these biologic molecules. It is important and clinically relevant to determine whether tetracycline and its other derivatives also counteract BMP functions. Animal models should be used to confirm these in vitro results.

Toll-like receptor (TLR)-mediated inflammatory response could negatively affect bone metabolism. In this study, we determined how osteogenesis is regulated during inflammatory responses that are downstream of TLR signaling. Human primary osteoblasts were cultured in collagen gels. Pam3CSK4 (P3C) and Escherichia coli lipopolysaccharide (EcLPS) were used as TLR2 and TLR4 ligand respectively. Porphyromonas gingivalis LPS having TLR2 activity with either TLR4 agonism (Pg1690) or TLR4 antagonism (Pg1449) and mutant E. coli LPS (LPxE/LPxF/WSK) were used. IL-1β, SH2-containing inositol phosphatase-1 (SHIP1) that has regulatory roles in osteogenesis, alkaline phosphatase and mineralization were analyzed. 3α-Aminocholestane (3AC) was used to inhibit SHIP1. Our results suggest that osteoblasts stimulated by P3C, poorly induced IL-1β but strongly upregulated SHIP1 and enhanced osteogenic mediators. On the contrary, EcLPS significantly induced IL-1β and osteogenic mediators were not induced. While Pg1690 downmodulated osteogenic mediators, Pg1449 enhanced osteogenic responses, suggesting that TLR4 signaling annuls osteogenesis even with TLR2 activity. Interestingly, mutant E. coli LPS that induces weak inflammation upregulated osteogenesis, but SHIP1 was not induced. Moreover, inhibiting SHIP1 significantly upregulated TLR2-mediated inflammatory response and downmodulated osteogenesis. In conclusion, these results suggest that induction of weak inflammatory response through TLR2 (with SHIP1 activity) and mutant TLR4 ligands could enhance osteogenesis.