Epithelial Innate Immune Response to Oral Bacteria

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DESCRIPTION: This application will analyze the molecular mechanisms utilized by host gingival epithelial cells (GECs) in response to commensal and pathogenic oral bacteria, and the cellular receptors and signaling pathways associated with innate immunity in the periodontium. GECs respond to bacteria in an interactive manner secreting chemokines and cytokines to alert various cell types and attract neutrophils. They also produce natural antimicrobial peptides of the beta-defensin family. The defensin antimicrobial peptides are part of the innate immune system, a complex set of responses that keeps microbial invaders in check and maintains the microbial ecology of the healthy periodontal pocket. Human beta-defensin-2 (hBD-2) expression is upregulated in GECs in response to both commensal and pathogenic bacteria. In addition, this peptide is widely expressed in normal oral mucosa, in contrast to normal epidermis, suggesting that the innate immune responses of normal oral epithelia are at a heightened state of readiness. This application will test the hypotheses that commensal and pathogenic oral bacteria stimulate different networks of genes in gingival epithelial cells (GECs), that commensals prime the state of innate immunity of GECs for increased responsiveness to the environment and to subsequent exposure to pathogens, and that p-defensins are a major influence in this heightened innate immune response. These hypotheses build on evidence that commensal and pathogenic bacteria utilize different signaling pathways for regulation of hBD-2 gene expression and that hBD-2 itself influences innate immune responses and acts as a positive autocrine regulator. Finally, new evidence suggests involvement of the proteinase-activated receptor (PAR) family in innate immune and inflammatory responses. These receptors signal the presence of danger in the environment and contribute to inflammation. A final Aim will examine the function of these receptors to signal in response to Porphyromonas gingivalis, a major periodontopathogen that has proteinases as part of its set of virulence factors. These questions and hypotheses will be examined with the goal to better understand the global responses of GECs to commensal vs. pathogenic bacteria emphasizing gene expression programs and receptors that are critical for innate immune responses. This work will lay the groundwork for identifying new therapeutic targets to prevent and treat periodontal diseases.