Gene expression arrays show that human epithelial cells and human arthritis-affected cartilage lack detectable amounts of mRNA for IL-1 antagonizing molecules: IL-1Ra and IL-1RII, but constitutively express IL-1. Functional genomic analysis was performed by reconstituting human IL-1RII expression in various IL-1RII-deficient cell types to examine its antagonist role using gene therapy approaches. Adenovirus-expressing IL-1RII when transduced into human and bovine chondrocytes, human and rabbit synovial cells, human epithelial cells, and rodent fibroblasts expressed membrane IL-1RII and spontaneously released functional soluble IL-1RII. The IL-1RII+ (but not IL-1RII−) cells were resistant to IL-1β-induced, NO, PGE2, IL-6, and IL-8 production or decreased proteoglycan synthesis. IL-1RII inhibited the function of IL-1 in chondrocytes and IL-1- and TNF-α-induced inflammatory mediators in human synovial and epithelial cells. IL-1RII+ chondrocytes were more resistant to induction of NO and PGE2 by IL-1β compared with IL-1RII− cells incubated with a 10-fold (weight) excess of soluble type II IL-1R (sIL-1RII) protein. In cocultures, IL-1RII+ synovial cells released sIL-1RII, which in a paracrine fashion protected chondrocytes from the effects of IL-1β. Furthermore, IL-1RII+ (but not IL-1RII−) chondrocytes when transplanted onto human osteoarthritis-affected cartilage in vitro, which showed spontaneous release of sIL-1RII for 20 days, inhibited the spontaneous production of NO and PGE2 in cartilage in ex vivo. In summary, reconstitution of IL-1RII in IL-1RII− cells using gene therapy approaches significantly protects cells against the autocrine and paracrine effects of IL-1 at the signaling and transcriptional levels.

Japan Arthritis Res Ther 2003, 5(Suppl 3):1 (DOI 10.1186/ar800) Apoptosis is a principal mechanism in metazoans by which superfluous or potentially harmful cells are eliminated. Deregulation of this process leads to a variety of diseases such as cancer and autoimmune diseases. Stimuli that can induce apoptosis are relatively diverse, and include the death factors (Fas ligand, tumor necrosis factor and TRAIL), DNA damage, and oxidative stress. Regardless of the origin of the apoptotic stimulus, commitment to apoptosis leads to activation of caspases, a family of cysteine proteases. Cleavage of a select group of cellular substrates by caspases is responsible for the morphological and biochemical changes that characterize apoptotic cell death. The degradation of nuclear DNA into nucleosomal units is one of the features of apoptotic cell death, and is mediated by a caspase-activated DNase (CAD). Cells deficient in CAD undergo cell death without the DNA fragmentation, but CAD-null mice did not show any adverse phenotypes. A close examination of the apoptotic cells in these mice indicated that apoptotic cells are always in macrophages. It seems that at an early stage of apoptosis, the dying cells present an 'eat me signal' on their surface. This signal is recognized by macrophages for engulfment, and DNase II in the lysosomes of macrophages degrades DNA of apoptotic cells. Mice deficient in both CAD and DNase II genes were established, and the development of various organs was found to be severely impaired in these mutant mice. The mice accumulated a large amount of undigested DNA in macrophages in various tissues during development. This accumulation of DNA in macrophages activated the innate immunity to induce the expression of the interferon β gene. The interferon thus produced seems to be responsible for the impaired tissue development. These results indicate that the degradation of DNA during apoptotic cell death is an essential step of apoptosis to maintain mammalian homeostasis. Osteoarthritis (OA) has been considered a biomechanically driven, degenerative disease of cartilage. However, the OA disease process affects not only the cartilage, but also the entire joint structure; and within the bone, cartilage and synovium of affected joints, profound metabolic changes transpire, which include the production of growth factors, nitric oxide (NO), prostaglandins (PGs), leukotrienes (LTs), IL-1β, tumor necrosis factor alpha, IL-6, and IL-8. The autocrine production of IL-1β by OA cartilage has been of particular interest, since both ex vivo human and in vivo animal studies indicate that IL-1 antagonists effectively attenuate cartilage degradation. Microarray technology has demonstrated differential expression in OA cartilage of a variety of IL-1-induced, NFβB-dependent genes. Among IL-β-induced products of OA cartilage are various eicosanoids, which include E 2 , PGD 2 , LTB 4 , PGF 1α , PGF 2α and thromboxane. Treatment of OA cartilage with cyclooxygenase (COX) inhibitors increases LTB 4 production threefold to five...