IL-4 and IL-13, but not IL-10, protect human synoviocytes from apoptosis

Interleukin-4, which has been contemplated for the treatment of rheumatoid arthritis and/or osteoarthritis because of its anti-catabolic properties, has also been shown to modulate apoptosis, Because inadequate apoptosis is thought to contribute to synovial hyperplasia, we have investigated the ability of IL-4 and other Th2 cytokines to protect human synovial cells from apoptosis, Human synoviocytes or synovial explants were pretreated with IL-4, IL-10, and IL-13 before exposure to NO donor sodium-nitro-prusside (SNP), Apoptosis was evaluated by microscopy, annexin V-FITC, 3-(4,5 dimethylthiazol-2-gl)-5-(3-carboxy-methoxylphenyl)-2-(4-sulphophenyl-2H tetrazolium inner salt (MTS) test, pulse held gel electrophoresis, and a method proposed in this study based on P-32 Klenow end labeling of high m,w, DNA, Pretreatment by IL-4 or IL-13, but not IL-10, protected human synoviocytes from apoptosis induced by SNP, Even at doses as high as 2 mM SNP, up to 86% and 56% protection was achieved, after IL-4 and IL-13 treatment, respectively. Cell survival,vas dependent on IL concentration. IL-4 and IL-13 also had anti-apoptotic effects on SNP-treated human synovial explants, Effects of IL-4 and IL-13 varied in the presence of phosphatidylinositol-3 kinase and protein kinase C inhibitors, implying the involvement of these pathways in antiapoptotic signaling. Antiapoptotic effects were dramatically inhibited by LY294002, and partially by the protein kinase C inhibitor Go 6976, while insulin-like growth factor increased synoviocyte survival. The possibility that IL-4 and IL-13 may enhance synovial expansion in vivo by their antiapoptotic effects is discussed.