Elevation of Serum Soluble Tumour Necrosis Factor Receptors in Patients with Polymyositis and Dermatomyositis

Abstract:

The aim of the study was, to examine the relationship between serum levels of soluble tumour necrosis factor receptors (sTNF-R) and the gene expression of two types of receptor for TNF (TNF-R), a 55 kDa receptor (TNF-R1) and a 75 kDa receptor (TNF-R2), in peripheral blood mononuclear cells (PBMC) from patients with polymyositis and dermatomyositis (PM/DM). Soluble tumour necrosis factor receptor 1 (sTNF-R1) and soluble tumour necrosis factor receptor 2 (sTNF-R2) levels in sera from patients were measured by enzyme-linked immunosorbent assay. Expression of TNF-R1 and TNF-R2 mRNAs in PBMC was analysed by Northern blotting. Serum sTNF-R1 and sTNF-R2 levels were elevated significantly in 25 patients with active-stage PM/DM, compared to those in 18 patients with inactive-stage PM/DM and 32 normal controls. Serum concentrations of sTNF-R1 and sTNF-R2 were correlated with PM/DM disease activity. TNF-R1 gene expression was enhanced in freshly isolated PBMC from patients with active-stage PM/DM. In contrast, TNF-R2 mRNA was expressed constitutively in patients with active-stage PM/DM and in normal controls. The expression of TNF-R1 and TNF-R2 mRNAs in PBMC and elevation of their soluble forms in the sera of patients with active-stage PM/DM suggest increased proteolytic cleavage of cell surface TNF-R from PBMC in patients with active-stage PM/DM, and that sTNF-R may regulate TNF-α-mediated muscle fibre damage in PM/DM.