In chronic inflammatory diseases like asthma or rheumatoid arthritis, erroneous and exaggerated accumulation of leukocytes in a tissue inadvertently causes the body harm. Several efficient anti-inflammatory drugs exist, for example corticosteroids and cyclo-oxygenase inhibitors. However, these drugs have potent and diverse effects and often act by inhibiting events subsequent to initiation of the inflammatory response, leading to more or less severe side-effects, especially when used in high doses for long periods of time. For this reason, strategies aimed at early inhibition of recruitment and activation of leukocytes have been suggested as safer and more specific approaches to reduce inflammation. Leukocyte adhesion to activated endothelium is a prerequisite to the following activation and extravasation, and takes place in the initial phase of inflammation. By using a model that allows leukocytes to adhere to tumour necrosis factor (TNF)-activated endothelial cells, thus mimicking aspects of an inflammatory reaction, we found that uridine, 4-thiouridine and isomaltitol could all reduce adhesion. This suggested that they may have anti-inflammatory potential. We therefore tried the three substances in a Sephadex-induced lung inflammation model and found that uridine and 4-thiouridine have several anti-inflammatory effects, such as being able to reduce leukocyte accumulation, decrease TNF protein levels and partly inhibit the oedema induced by Sephadex. Isomaltitol turned out to have immunomodulating, rather than anti-inflammatory, effects, which could be of interest in diseases where inadequate inflammatory responses are a problem.

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