"Enzyme Blockers May Prove Useful Against Inflammatory Myopathies"

Polymyositis (PM) and sporadic inclusion body myositis (sIBM) are autoimmune diseases that occur when the body's immune system mistakenly targets muscle tissue for destruction. These diseases may cause weakness, pain and fatigue, and have a fluctuating course. Researchers believe that much of the muscle inflammation that occurs in these diseases is mediated by a type of immune cell called a T cell. Under normal circumstances, T cells destroy other cells in the body that have been invaded by viruses or bacteria. In the inflammatory myopathies, however, T cells target healthy muscle cells.

In order to trigger an inflammatory response, T cells must first leave the bloodstream and make their way to the affected organ. Some researchers see this requirement as a target at which to aim therapies against inflammatory muscle diseases.

Recently, Young-Chul Choi and Marinos Dalakas of the National Institute of Health found evidence that enzymes called matrix metalloproteinases, or MMPs, play a role in helping destructive T-cells leave the bloodstream and stick to muscle cells in PM and sIBM. These same enzymes may play a role in other autoimmune diseases such as multiple sclerosis, Guillain-Barré syndrome and rheumatoid arthritis.

The researchers conclude that MMP blockers might be used to prevent T cells from invading the muscle tissue, and should be considered in clinical trials of patients with inflammatory myopathies. The work appeared in the Jan. 11 issue of Neurology.