Dual biological functions of an interleukin-1 receptor antagonist–interleukin-10 fusion protein and its suppressive effects on joint inflammation

The aim of this study was to construct and purify a novel interleukin-1 receptor antagonist (IL-1ra)–interleukin-10 (IL-10) fusion protein and determine its biological function and anti-inflammatory effects. The isolated cDNAs of two inhibitory cytokines (IL-1ra, IL-10) were used to construct a cDNA for the IL-1ra–IL-10 fusion protein. The expressed recombinant cytokines and fusion product were purified and their biological properties analysed. The anti-IL-1 effect was evaluated by using a thymocyte-proliferation assay, and the IL-10 effect was investigated by the inhibition of interferon-γ (IFN-γ) production from splenocytes. The clinical response and histological analyses were studied in an adjuvant arthritic rat model. The fusion protein was 38 000 molecular weight in size. Sodium dodecyl sulphate–polyacrylamide gel electrophoresis (SDS–PAGE) and immunoblotting demonstrated that the purified protein was recognized by both IL-1ra and IL-10 antibodies. The fusion protein significantly inhibited IL-1-mediated thymocyte proliferation and concanavalin A (ConA)-primed IFN-γ production from splenocytes. The fusion protein also suppressed joint swelling (paw circumference reduced from 5·0 ± 0·2 to 4·1 ± 0·1 cm; paw thickness ≈ 2 mm in difference) and synovial inflammation in adjuvant arthritis of rats. Our investigations indicate that this fusion protein effectively suppresses inflammatory arthritis and may initiate a trend for future clinical application to target multiple molecules at the same time

Increased interleukin-10 production and Th2 skewing in the absence of 5-lipoxygenase

Eicosanoids (prostaglandins and leukotrienes) are important mediators of inflammatory responses. These lipid mediators may also regulate the production of peptide mediators of the immune system. In this study, we investigated the effect of the absence of 5-lipoxygenase (5-LO)-derived leukotrienes on interleukin (IL)-10 production. IL-10 is a key regulator of immune and inflammatory responses, and previous studies have suggested that prostaglandins effect their immunosuppressive functions in part by stimulation of IL-10 production. We therefore investigated whether leukotriene production would have a similar role in regulation of IL-10 production. We have made the striking observation that absence of 5-LO-derived leukotrienes results in increased IL-10 production with a concomitant decrease in the production of pro-inflammatory cytokines, including tumour necrosis factor (TNF)-α and IL-12. Moreover, T-cell cytokine production in the absence of 5-LO-derived leukotrienes results in increased IL-4 production and decreased interferon (IFN)-γ production. This may be in part secondary to increased IL-10 production and its effects on dendritic cell function resulting in altered T-cell differentiation. These findings indicate that, in addition to the central role leukotrienes play in the acute inflammatory response, endogenous leukotrienes are also important regulators of inflammatory cytokine production, via regulation of IL-10 production and in vivo differentiation of T cells