Thrombin in inflammation and healing: relevance to rheumatoid arthritis

The enzyme thrombin appears to have a role in both the inflammatory and healing process of rheumatoid arthritis (RA). RA is a systemic disease usually affecting the joints. Thrombin aids in the formation of blood clots. It causes plate aggregation leading to blood coagulation. Thrombin contributes to the inflammatory process by upregulating the synthesis of arachidonic acid. This leads to the proliferation of synovial cells in joints affected by RA. Fibroblasts may inhibit the inflammatory effects by releasing the thrombin inhibitor PN-1 in a dose-dependent relationship. In addition, thrombin and basic fibroblast growth factors can collectively initiate healing through cellular proliferation and angiogenesis, the development of blood vessels.