In periodontal pockets, PMN form a protective barrier between pathogenic microorganisms and the underlying connective tissue. Their function is crucial for host protection from infection throughout the oral cavity and for promotion of wound healing. Mediators found at oral inflammatory sites induce expression of a limited number of cytokine genes in PMN that regulate inflammation, immunity, and tissue repair. For example, TNF and GM-CSF rapidly and transiently induce IL-1Beta expression in PMN. There is a direct correlation between transcription and relative levels of TNF-induced IL-1Beta mRNA and protein levels in PMN. In contrast, in fibroblasts TNF induces IL-1Beta mRVA via message stabilization. Expression of cytokines is initiated by inducing agents that are perceived by cell surface receptors. Clearly, there are differences between PMN and fibroblasts in how these signals are transduced to induce IL-1Beta expression. Although little is known about signal transduction mechanisms regulating gene expression in PMN, protein kinase C and Ca2+ appear to be critical for TNF induction of IL-1Beta. The objective of these studies is to determine how receptor binding of cytokines leads to induction of IL-1Beta transcription in PMN. IL-1Beta is worthy of study because of its key role in regulating bone resorption, collagen degradation, immune responses, and recruitment of inflammatory cells in periodontal disease and other oral inflammatory disorders. GM-CSF and TNF have been chosen as inducing agents because they are important in the regulation of inflammation, PMN gene expression, and have been recently used in clinical trials to modulate inflammation and immunity. Hypothesis: In PMN, the induction of IL-1Beta transcription by TNF is primarily regulated by Ca2+ and protein kinase C, while GM-CSF induces IL-1Beta transcription via tyrosine protein kinases and protein kinase C. These signaling pathways play key roles in modulating inflammation by controlling transcription of cytokine genes. This regulates the specificity, magnitude, and kindeics of the response.
Specific aim I : Determine the early events in signaling for IL-1Beta expression by TNF and GM-CSF in human PMN by using agonists and antagonists of signaling pathways to inhibit mRNA expression and transcription.
Specific aim II : Confirm the activation of PC and Tyrosine protein kinase by TNF and GM-CSF and delineate the activation of downstream signal transducers (e.g., ras-related proteins, Raf, and MAP kinase).
Specific aim III. Characterize TNF- and GM-CSF-induced IL-1Beta transcription factors. Variation in the pattern of cytokine gene expression in response to the same inducing agent provides the basis for a tissue specific response. It also provides a potential target for specifically modulating the response. Understanding the pathways that lead to gene expression in specific cell types, like PMN, will be critical in determining which agents may be effective and what their effects will be in the host.
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