Specific therapies are not currently available for systemic autoimmune rheumatic diseases. Development of specific and effective therapies requires the definition of pathways important in the disease pathogcncsis. The MHC class 1 mouse model of myositis is a powerful tool to identify such pathways. The long term goals of this proposal are to define the molecular pathways responsible for the skeletal muscle damage and dysfunction in autoimmune myositis. The MHC class I transgenic mice develop several features of human autoimmune polymyositis including myositis-specific autoantibodies. Preliminary experiments showed that the absence of lymphocytes and macrophages only partially ameliorates muscle fiber damage and dysfunction suggesting that over-expression of MHC class I in myofibers also initiates a specific sequence of ceil autonomous (myofiber) pathways leading to muscle damage. Thus, in this model both immune cells and skeletal muscle cells appear to play a role in the manifestation of full blown autoimmune myositis. Therefore, we propose that skeletal muscle cell damage in MHC class I expressing muscle fibers can partly be induced by cytotoxic T lymphocytes and partly by perturbation of intracellular homeostasis (ER stress response). Our preliminary experiments clearly show that the ER stress response pathway is highly up-regulated in both human myositis and in the mouse model. Defining the contribution of mechanisms of ER stress response and NF-kB pathways in MHC class I-expressing fibers and their role in muscle fiber damage and dysfunction is a major priority of this proposal. This hypothesis is pursued by a) blocking critical members of ER stress response pathway and NF-kB pathways in vivo, and b) identifying novel immune and non-immune pathways mediating muscle fiber damage and dysfunction by gene and protein expression profiling. The proposed aims will not only define predominant mechanisms of muscle fiber damage and dysfunction in vivo in transgenic mice but will also potentially identify new targets for therapeutic intervention in human myositis.

Agency
National Institute of Health (NIH)
Institute
National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS)
Type
Research Project (R01)
Project #
5R01AR050478-05
Application #
7391060
Study Section
Special Emphasis Panel (ZRG1-MOSS-D (04))
Program Officer
Mancini, Marie
Project Start
2005-04-01
Project End
2010-01-31
Budget Start
2008-02-01
Budget End
2009-01-31
Support Year
5
Fiscal Year
2008
Total Cost
$339,350
Indirect Cost
Name
Children's Research Institute
Department
Type
DUNS #
143983562
City
Washington
State
DC
Country
United States
Zip Code
20010
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