Joint inflammation and cartilage destruction may occur uncoupled

WB van den Berg - Springer seminars in immunopathology, 1998 - Springer
WB van den Berg
Springer seminars in immunopathology, 1998Springer
Chronic arthritis is characterized by a persistent joint inflammation and concomitant joint
destruction. Although the joint swelling is a major clinical problem, destruction of bone and
cartilage may occur uncoupled to inflammation and it is of utmost importance to fully
understand the elements of the destructive process. TNF and IL-1 are considered master
cytokines in the process of human RA, with a claimed cascade of TNF inducing most of the
IL-1 production. Studies in experimental models revealed that TNF is indeed a pivotal …
Abstract
Chronic arthritis is characterized by a persistent joint inflammation and concomitant joint destruction. Although the joint swelling is a major clinical problem, destruction of bone and cartilage may occur uncoupled to inflammation and it is of utmost importance to fully understand the elements of the destructive process. TNF and IL-1 are considered master cytokines in the process of human RA, with a claimed cascade of TNF inducing most of the IL-1 production. Studies in experimental models revealed that TNF is indeed a pivotal cytokine in joint swelling, yet IL-1 is the dominant cartilage destructive cytokine and its production may occur independent of TNF. This was found with anti-TNF/IL-1 neutralizing antibodies and the observations were recently backed up with similar data in arthritis models in TNF and IL-1 knockout mice. Apart from the absolute level of IL-1, the destructive potential of an arthritis is determined by the balance with regulatory cytokines and anabolic growth factors. IL-4, IL-6, and IL-10 can promote inflammation and tissue fibrosis, yet cartilage destruction is found to be greatly reduced by these cytokines, linked to a range of pathways which can reduce the IL-1 impact on the articular cartilage. Finally, the presence of anabolic growth factors in the inflamed synovium may have a major impact on net destruction. Endogenous transforming growth factor-β (TGF-β) is found in inflamed synovia, but local coadministration of TGF-β further enhanced the degree of synovitis, yet almost fully prevented cartilage damage, providing another example of a major lack of correlation between inflammatory mass and destructive potential. It is suggested that novel therapy in RA patients should not only focus on reduction of outer signs of joint inflammation, but should also include attempts at reduction of cartilage destruction.
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