Danger signal molecule extracellular ATP (eATP) is released by infected cells and becomes metabolized to adenosine by multiple enzymatic steps, one of which is catalyzed by CD73, a surface-bound enzyme that converts adenosine monophosphate (AMP) to adenosine. This AMP hydrolysis by CD73 is an irreversible rate- limiting step in adenosine signaling that is often referred to as ?an immunological switch? from pro-inflammatory (eATP) to anti-inflammatory (adenosine) mediator. Porphyromonas gingivalis is a keystone pathogen strongly associated with severe periodontal disease and can use multiple mechanisms to successfully invade, replicate, and disseminate within and through the human gingival epithelial cells (GECs), a major arm of initial defenses in mucosal surfaces. Despite the growing significance in various pathological states including cancer, inflammatory diseases, and recently cellular infection, the role of CD73 for regulating host immune response and bacterial infection in the oral cavity is not well understood. Our laboratory previously showed that P. gingivalis can inhibit eATP-mediated reactive oxygen species (ROS) generation by NADPH oxidase 2 and that the bacterial growth is modulated and enhanced by adenosine 2a receptor-coupled adenosine signaling in GECs. Our novel preliminary findings also revealed significantly increased CD73 expression with P. gingivalis in GECs. Furthermore, CD73-mediated signaling specifically impacted on the P. gingivalis intracellular survival, inhibited ROS generation, and dampened the gene expression of interleukin-6 (IL-6) whose addition led to decreased levels of P. gingivalis in GECs. Thus, our overarching hypothesis is that P. gingivalis can selectively regulate host CD73-mediated immune signaling pathways for affluent intracellular growth and survival in the gingival epithelium. We will test our hypothesis through completion of the following specific aims.
Specific Aim 1 will establish the regulatory role of CD73 for P. gingivalis intracellular infection by further investigating functional importance supporting the P. gingivalis/CD73 coupled signaling in the GECs.
Specific Aim 2 will elucidate select cellular and molecular mechanisms by which CD73 modulates P. gingivalis intracellular growth and survival, specifically through interfering with pro-inflammatory IL-6 signaling.
Both aims will use primary GECs model system to functionally dissect out mechanisms and define the molecular events. Hence, this proposal will characterize novel physiologically relevant modulator(s) of oral bacterial infection and reveal the multidirectional cross-talk between host CD73/P. gingivalis/IL-6 axis for the modulation of intracellular P. gingivalis infection in the host cells. The results of this study will provide fundamentally novel molecular understanding of P. gingivalis persistence mechanisms in the oral mucosa and may ultimately contribute to future development of effective therapeutics for controlling P. gingivalis associated infections. This fellowship will also provide training in oral microbiology/immunology and will foster the development of the trainee into a unique and critically needed oral health academic clinician/scientist.
Porphyromonas gingivalis is a key microorganism in periodontal disease which affects more than 47% of the adult American population. We have discovered that CD73, a surface-bound enzyme that generates anti- inflammatory molecule adenosine, can modulate P. gingivalis intracellular growth and survival in the human gingival epithelial (gum) cells. This study will elucidate novel host molecular mechanisms that may alter the outcome of infection in gum cells, paving the way to the future development of therapeutics for P. gingivalis associated diseases.
