Balancing expression of PRRs in epithelial innate immune responses to bacteria

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Abstract Epithelial tissues function as the first line of defense between the host and the outside environment, which includes pathogenic and non-pathogenic bacteria. In the oral cavity, epithelial tissues are constantly exposed to a variety of bacteria, but most individuals maintain a healthy homeostasis. However, little is known about how this homeostatic relationship is orchestrated. Preliminary data utilizing RNA interference via siRNA suggest that compensatory mechanisms exist among Pattern Recognition Receptors (PRRs). Additionally, when a PRR is activated, the expression of other PRRs increases. These data strongly suggest that epithelial cells have novel mechanisms to balance expression of PRRs in response to bacteria. The hypothesis to be tested in this proposal is that PRRs balance their responses in epithelial innate immunity upon exposure to oral bacteria depending on the characteristics and pathogenicity of the bacteria. The goal of this work is to understand cross- communication between epithelial receptors as well as the specific signaling pathways that are involved in the PRR cross-communication in epithelial innate immunity. This proposal will investigate how various epithelial cell receptors compensate for the activation or absence of one another in inducing appropriate epithelial innate immune responses. In addition, this proposal will examine if activation of PRRs differentially regulate the NF¿B and MAPK signaling pathways, thus tailoring epithelial innate immune responses to individual bacterium. Since bacteria have multiple Microbial-Associated Molecular Patterns and epithelial cells express multiple PRRs, it is reasonable to expect that there is cross-communication and balancing between these PRRs in epithelial responses to various bacteria in order to induce appropriate innate immune responses. The proposed studies will lead to a better understanding of the way oral epithelia produce appropriate innate immune responses to pathogenic and non-pathogenic bacteria, guiding a way to new therapeutic targets to prevent and treat oral diseases, such as periodontal disease.