Evaluation of the anti-inflammatory effects of the interleukin-1 receptor antagonist protein in equine synovial fluid using flow cytometric techniques / Avaliação dos efeitos antiinflamatórios da proteína antagonista de receptor de interleucina - 1 (IRAP) por citometria de fluxo em líquido sinovial de eqüino

Patrícia Monaco Brossi

Joint disease in horses, specifically osteoarthritis, is one of the most prevalent and debilitating illnesses affecting equine industry and for this reason continued research and improvements in therapeutics are needed. Osteoarthritis is a degenerative disease that can be triggered by a number of factors and where ultimately all articular tissues are affected. The hallmark of osteoarthritis is the degeneration of the articular cartilage matrix, where the most relevant and expressive events take place. In the development of osteoarthritis there is disruption in extracellular matrix homeostasis with an overall balance toward cartilage metabolism. Homeostasis of the articular environment relies on balance between anabolic and catabolic events and results in ability of cartilage to respond to molecular or mechanical cues. This apparently antagonic processes are orquestrated by soluble protein mediators, for example the anabolic insulin-like growth factor-I (IGF-I), and, on the other side, by inflammatory cytokines, which in turn, are implicated in degradative processes of articular cartilage, characteristic of osteoarthritis. They deplete cartilage matrix from collagen and proteoglycans and the classical example of such a cytokine is interleukin-1. Interleukin-1 has a central role in the physiopathologic processes of osteoarthritis and has been implicated in the genesis of a number of catabolic events when acting on chondrocytes and synoviocytes. Examples are gene induction for metalloproteinases and agrecanases production, as well as production of other inflammatory mediators like ciclooxygenase, prostaglandin E2 and oxygen-derived reactive species. Its biological effects are observed after interaction with two different but specific types of receptors and are modulated by the occurrence of a natural antagonist, the interleukin-1 receptor antagonist protein (IRAP). In the present study the anti-inflammatory effects of this antagonist protein were evaluated in synovial fluid using cytometric flow techniques. It was observed that: 1- addition of IRAP to synovial fluid cells stimulated in vitro by LPS and PMA reduced the production of oxygen-derived reactive species; 2- plasma, used as a control, exhibited similar effects on activated synovial cells when compared to IRAP in vitro 3- the anti-inflammatory effect is due, in its majority, to the variation in intensity of oxygen-derived reactive species, more than on fluctuations on the percentage of synovial fluid cells actively engaged in its generation in vitro. These results support the therapeutic aplicability of IRAP® for its anti-inflammatory effect observed on synovial fluid cells evaluated with flow cytometric techniques. They also corroborate to the usefulness of cytometric flow techniques in equine synovial fluid cells; they are an invaluable tool to evaluate quantitative and qualitatively the production of oxygen-derived reactive species mediated by their activation with PMA and LPS.

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