Tobacco Upregulates P. gingivalis Fimbrial Proteins Which Induce TLR2 Hyposensitivity

Tobacco smokers are more susceptible to periodontitis than non-smokers but exhibit reduced signs of clinical inflammation. The underlying mechanisms are unknown. We have previously shown that cigarette smoke extract (CSE) represents an environmental stress to which P. gingivalis adapts by altering the expression of several virulence factors - including major and minor fimbrial antigens (FimA and Mfa1, respectively) and capsule - concomitant with a reduced pro-inflammatory potential of intact P. gingivalis.We hypothesized that CSE-regulation of capsule and fimbrial genes is reflected at the ultrastructural and functional levels, alters the nature of host-pathogen interactions, and contributes to the reduced pro- inflammatory potential of smoke exposed P. gingivalis. CSE induced ultrastructural alterations were determined by electron microscopy, confirmed by Western blot and physiological consequences studied in open-flow biofilms. Inflammatory profiling of specific CSE-dysregulated proteins, rFimA and rMfa1, was determined by quantifying cytokine induction in primary human innate and OBA-9 cells. CSE up-regulates P. gingivalis FimA at the protein level, suppresses the production of capsular polysaccharides at the ultrastructural level, and creates conditions that promote biofilm formation. We further show that while FimA is recognized by TLR2/6, it has only minimal inflammatory activity in several cell types. Furthermore, FimA stimulation chronically abrogates the pro-inflammatory response to subsequent TLR2 stimulation by other TLR-2-specific agonists (Pam3CSK4, FSL, Mfa1) in an IkappaBalpha- and IRAK-1-dependent manner.These studies provide some of the first information to explain, mechanistically, how tobacco smoke changes the P. gingivalis phenotype in a manner likely to promote P. gingivalis colonization and infection while simultaneously reducing the host response to this major mucosal pathogen

Porphyromonas gingivalis–dendritic cell interactions: consequences for coronary artery disease

An estimated 80 million US adults have one or more types of cardiovascular diseases. Atherosclerosis is the single most important contributor to cardiovascular diseases; however, only 50% of atherosclerosis patients have currently identified risk factors. Chronic periodontitis, a common inflammatory disease, is linked to an increased cardiovascular risk. Dendritic cells (DCs) are potent antigen presenting cells that infiltrate arterial walls and may destabilize atherosclerotic plaques in cardiovascular disease. While the source of these DCs in atherosclerotic plaques is presently unclear, we propose that dermal DCs from peripheral inflamed sites such as CP tissues are a potential source. This review will examine the role of the opportunistic oral pathogen Porphyromonas gingivalis in invading DCs and stimulating their mobilization and misdirection through the bloodstream. Based on our published observations, combined with some new data, as well as a focused review of the literature we will propose a model for how P. gingivalis may exploit DCs to gain access to systemic circulation and contribute to coronary artery disease. Our published evidence supports a significant role for P. gingivalis in subverting normal DC function, promoting a semimature, highly migratory, and immunosuppressive DC phenotype that contributes to the inflammatory development of atherosclerosis and, eventually, plaque rupture

Porphyromonas gingivalis Fimbriae Proactively Modulate β(2) Integrin Adhesive Activity and Promote Binding to and Internalization by Macrophages

In monocytes, the fimbriae of the oral pathogen Porphyromonas gingivalis activate cross talk signaling from Toll-like receptor 2 (TLR2) to the β(2) integrin CD11b/CD18, leading to the induction of the high-affinity state of the latter receptor. CD14 plays an important role in this “inside-out” proadhesive pathway by binding fimbriae and facilitating the activation of TLR2 and phosphatidylinositol 3-kinase signaling. In its high-affinity state, CD11b/CD18 mediates monocyte adhesion to endothelial cells and transmigration to sites of infection. We have now shown that P. gingivalis fimbriae function as both an activator and a ligand of CD11b/CD18; thus, fimbriae proactively promote their own binding to monocytes. Indeed, treatments that interfered with fimbria-induced activation of CD11b/CD18 (i.e., blockade of CD14, TLR2, or phosphatidylinositol 3-kinase signaling) also suppressed the cell binding activity of fimbriae, which was largely inducible and CD11b/CD18 dependent. Development of a recombinant inside-out signaling system in Chinese hamster ovary cells confirmed the ability of fimbriae to activate CD14/TLR2 signaling and induce their own CD11b/CD18-dependent binding. Induction of this proadhesive pathway by P. gingivalis fimbriae appeared to take place in lipid rafts. Indeed, methyl-β-cyclodextrin, a cholesterol-sequestering agent that disrupts lipid raft organization, was found to inhibit the fimbria-induced assembly of CD14/TLR2 signaling complexes and the activation of the high-affinity state of CD11b/CD18. Experiments using macrophages from mice deficient in various pattern recognition receptors indicated that the receptors involved in the inside-out proadhesive pathway (CD14, TLR2, and CD11b/CD18) are important for mediating P. gingivalis internalization within macrophages. It therefore appears that P. gingivalis proactively modulates β(2) integrin adhesive activity for intracellular uptake