While glial cells are recognized for their roles in maintaining neuronal function, there is growing appreciation of the ability of resident brain cells to initiate and/or regulate inflammation following trauma or infection in the central nervous system (CNS). We have previously demonstrated the ability of astrocytes and microglia, resident glial cells of the CNS, to respond to bacterial pathogens by the rapid production of an array of inflammatory mediators. Furthermore, published work from our laboratory have shed light on the possible mechanisms that underlie glial activation with the demonstration that these cells express members of the Toll- like family of receptors (TLR) for conserved bacterial motifs. Interestingly, recent studies suggest that TLR can act in synergy with members of the novel nucleotide-binding oligomerization domain (NOD) family of proteins to augment the immune responses of leukocytes to bacterial pathogens. We have recently completed investigations showing that astrocytes and microglia can express NOD2 that can act as a specific pattern recognition receptor for discrete bacterial peptidoglycan motifs. Importantly, we have demonstrated that specific ligands for NOD2 receptors can synergistically augment TLR-mediated production of the key inflammatory cytokines, IL-1 beta, IL-6 and TNF-alpha. In the proposed studies we will assess the role of NOD2 proteins in the initiation and/or maintenance of inflammatory immune responses of glia to clinically relevant bacterial pathogens of the CNS. We will employ isolated cultures of astrocytes and microglia derived from normal animals and mice genetically deficient in the expression of NOD2 to assess the relative importance of this novel receptor in cytokine production following in vitro exposure to Neisseria meningitidis, and Staphylococcus aureus. Furthermore, we will administer N. meningitidis, and S. aureus via intracerebroventricular injection into wild type and NOD2 deficient mice animals and assess subsequent bacterial burden and inflammatory CNS damage following infection to determine the relative importance of NOD2 in the progression of infection and/or CNS inflammatory damage in an in vivo setting. Results from these studies are anticipated to reveal that this NOD molecule represents an important mechanism underlying the initiation and/or maintenance of immune responses during bacterial CNS infections and will contribute significantly to our understanding of the events that underlie the development of either protective host responses within the brain or the progression of damaging CNS inflammation. Importantly, these initial studies will provide a solid rationale for more comprehensive investigations into the regulation and role of this novel microbial pattern recognition receptor during CNS infection for which future R01 mechanism funding will be sought. There is growing appreciation of the ability of resident brain cells to initiate and/or regulate inflammation following trauma or infection in the central nervous system (CNS). Work from our laboratory has shed light on the possible mechanisms that underlie glial activation with the demonstration that these cells express members of the novel nucleotide-binding oligomerization domain (NOD) family of proteins that can act in synergy with Toll-like pattern recognition receptors to augment the immune responses of leukocytes to bacterial pathogens. In the proposed studies we will assess the role of NOD2 proteins in the initiation and/or maintenance of inflammatory immune responses of glia to clinically relevant bacterial pathogens of the CNS. Results from these studies will contribute significantly to our understanding of the events that underlie the development of either protective host responses within the brain or the progression of damaging CNS inflammation. ? ? ?
