The long-term goals of the proposed studies are to understand the cellular/molecular mechanisms regulating neuronal-glial interactions during temporomandibular joint (TMJ) pathology and therapy. Neuronal-glial interactions play a key role during inflammation and pain yet the cellular mechanisms are not well understood. The proposed studies will focus on the roles of calcitonin gene-related peptide (CGRP), nitric oxide (NO), and mitogen-activated protein (MAP) kinases in initiating and maintaining TMJ inflammation. Elevated levels of the neuropeptide CGRP and multifunctional signaling molecule NO in synovial fluid of arthritic TMJs correlate with chronic inflammation and pain and contribute to TMJ degeneration. Recently, MAP kinases have been reported to be important in the underlying pathology of inflammatory diseases. We will test the hypothesis that neuronal release of CGRP activates trigeminal glial cells causing increases in secondary messengers and induction of specific MAP kinases and iNOS that stimulate production and release of NO. Importantly, we have shown that NO increases CGRP synthesis and release from trigeminal neurons. Thus, we will investigate the cellular mechanisms involved in neuronal-glial interactions that help to sustain a pathological inflammatory cycle central to chronic inflammation and pain associated with TMJ disorders (TMD). In addition, we will determine the role of MAP kinase phosphatases, which function to regulate MAP kinase activity and thus, reduce inflammation. To accomplish these goals, primary cultures of trigeminal ganglia and trigeminal ganglia organ cultures as well as in vivo studies in a model of TMJ inflammation will be utilized. Results from these studies will provide insight into the molecular mechanisms by which CGRP release from trigeminal neurons modulates iNOS gene expression in glial cells that is likely to facilitate identification of new molecular targets for treating TMD and other orofacial diseases. It is estimated that 11 million American adults now suffer from symptoms attributed to TMD. Since TMD predominantly affects women of childbearing age and can be associated with significant morbidity, these disorders have significant social and economic ramifications. In the search for new treatment modalities to treat acute inflammation and chronic pain, a thorough understanding of the signaling molecules and pathways involved in neuronal and glial cell activation within the trigeminal ganglion would be beneficial.
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