A synthetic corticosteroid, dexamethasone regulates generation of soluble form of interleukin-6 receptor of human lymphocytes, in vitro.

In contrast to most of the soluble cytokine receptor antagonists properties, the soluble IL-6 receptor (sIL-6R) occurring in various body fluids of healthy persons and patients with various diseases is an agonist. The enhancing effect is due to its ability to form complex with IL-6 and to bind to gp130 making constitutively IL-6 receptor negative cells responsive for IL-6. The generation as well as the functional role of soluble IL-6 receptor is poorly understood. Earlier, we found that the sIL-6R levels in sera of patients with systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA) were higher than those of the control group measured by ELISA sandwich technology. In the present study we detected different levels of sIL-6R in the supernatants of lymphocyte cultures of healthy persons and patients with RA as well as SLE. Moreover, we found, that in vitro dexamethasone treatment stimulated generation of sIL-6R in both healthy persons and in active SLE, while it strongly suppressed production of sIL-6R in both RA groups. At mRNA level, we found that in SLE both the IL-6R mRNA encoding the membrane spanning and alternatively spliced (soluble) variants increased. Surprisingly, the strong decrease of sIL6R protein in RA was not found at mRNA level.