The effects of cyclosporin A on bone and cartilage.

Cyclosporin A (CyA) is a potent immunomodulatory agent with an increasing number of clinical applications. Although its precise mechanisms of action are yet to be elucidated, one of the most important known properties of CyA is its ability to inhibit the production of cytokines involved in the regulation of T cell activation. There is also evidence for direct effects on other cell types, such as B cells, macrophages, and bone and cartilage cells. The effects of CyA on T cells and on bone, cartilage and synovial cells, which can produce a range of cytokines, are of interest in the study of inflammatory diseases such as RA. It has been shown, for example, that in vitro CyA inhibits bone resorption induced by interleukin-1, 1,25-dihydroxy-vitamin D3, parathyroid hormone and prostaglandin E2. In vivo, it protects against adjuvant arthritis.