The objectives of this study are to understand the precise function of protein kinase D1 (PKD1) in the Toll- like receptor (TLR)/interleukin-1 receptor (IL-1R) signaling pathway and to develop an effective and safe way to suppress the vicious cycle of inflammation in arthritic joints by interfering with TLR/IL-1R signal transduction using nanosome-based local delivery of inhibitory peptides. Rheumatoid arthritis (RA) is an autoimmune disease manifested by chronic inflammation, swollen joints, development of auto-reactive T-lymphocytes, and destruction of cartilage and bone in joints. While the factors that initiate and perpetuate inflammation are not well understood, it is thought that RA may be initiated in part by signaling through TLRs that contribute to the development of a self-perpetuating reaction leading to chronic inflammation and development of pathogenic auto-reactive Th1/Th17 cells. Therefore, disruption of the signaling pathway used by most TLRs may provide an opportunity to halt the RA process in the earliest stages of development before irreversible joint damage occurs. Preliminary studies show that systemic suppression of PKD1 activation substantially ameliorates arthritis in murine models. Also, that PKD1 is constitutively activated in RA synoviocytes and is responsible for expression of proinflammatory mediators by those cells. These findings support our hypothesis that PKD1 is a critical factor for development of proinflammatory reactions in the joint and might be an effective molecular target for therapeutic intervention. We have shown that following stimulation with MyD88-dependent TLR/IL-1R ligands, PKD1 (a serine/threonine kinase) is recruited to and activated within the cognate receptor complex. Activation of PKD1 in TLR/IL-1R signaling is down-stream of IRAK4 and IRAK1, but up-stream of TRAF6 ubiquitination. However, the specific domains of PKD1 that allow assembly of the receptor complex and the function of PKD1 in TLR/IL-1R signal transduction have not been established. Our goals are to define the molecular mechanism of PKD1 activation and action in TLR/IL-1R signaling, to identify the specific domains of PKD1 that allow for assembly of the IRAK4/IRAK1/PKD1/TRAF6 complex that can be applied to the development of a novel approach to inhibit PKD1 activation in a TLR/IL-1R pathway-specific manner, and to selectively deliver a therapeutic agent (that blocks TLR/IL-1R signal transduction) to the inflamed arthritic joints using an innovative target-specific drug delivery system. Specifically we will 1) determine the activation and action mechanisms of PKD1 in TLR/IL-1R signaling;2) develop nanosomes that can deliver a therapeutic dose of peptide-based inhibitors of PKD1 activation to inflamed joints;and 3) test the hypothesis that delivery of a specific inhibitor of PKD1 activation targeted to inflammatory macrophages/monocytes will effectively alter the inflammatory milieu and prevent arthritis in an animal model. The results could be translated into an innovative therapeutic approach to effectively control RA progression with fewer side effects than current regimens.

Public Health Relevance

It is currently thought that rheumatoid arthritis (RA) may be initiated in part by signaling through Toll-like receptors (TLRs) and the interleukin-1 receptor (I-1R), contributing to a self-reinforcing reaction leading to chronic inflammation and development of pathogenic autoimmunity in joints. Disruption of a major molecular signaling pathway utilized in common by these receptors may provide a way to prevent chronic inflammation and RA progression before irreversible joint damage occurs. Therefore, we propose to develop a new way to interrupt signal transduction of the TLR/IL-1R pathway and to selectively deliver a therapeutic agent to the inflamed arthritic joints using an innovative target-specific drug deliver system that can be translated into a therapeutic approach to effectively control the progress of RA, with fewer adverse effects than conventional therapies.

National Institute of Health (NIH)
National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS)
Research Project (R01)
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Arthritis, Connective Tissue and Skin Study Section (ACTS)
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Mao, Su-Yau
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University of Tennessee Health Science Center
Schools of Medicine
United States
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