Abstract

Objective: To evaluate the effect of tumour necrosis factor α (TNFα), interleukin (IL) 1β, and their respective inhibitors the p75 TNFα soluble receptor (sTNFR) and the type II sIL1βR (sIL1RII) on whole muscle and isolated myoblast activation.

Methods: Normal muscle samples were stimulated for 7 days with TNFα alone or in combination with IL1β, and myoblasts from these samples for 48 hours. IL6 production was measured by ELISA. Nuclear translocation of NF-κB was analysed by immunofluorescent staining and class I MHC expression by FACS.

Results: TNFα and IL1β induced IL6 production by normal muscle samples and myoblasts, the action of TNFα being more potent on muscle samples. Their soluble receptors (1 μg/ml) decreased this production. Suboptimal concentrations of TNFα and IL1β induced NF-κB translocation. sTNFR markedly down regulated TNFα-induced translocation while sIL1RII was less potent on IL1β-induced activation. NF-κB translocation induced by the combination of optimal concentrations of TNFα and IL1β was completely inhibited by their soluble receptors. TNFα and to a lesser extent IL1β induced class I MHC expression by myoblasts and this effect was completely inhibited by their respective soluble receptors.

Conclusion: These results suggest that TNFα and IL1β should be targeted for myositis treatment.