Influence of cytokines on the density of beta 2-adrenergic receptors on peripheral blood mononuclear cells in vitro.

Previous investigations have demonstrated a decrease of the number of beta 2-adrenergic receptors (beta 2R) on peripheral blood mononuclear cells (PBMC) in patients with rheumatic diseases that correlated with the systemic inflammatory activity. However, the main factor(s) modulating the beta 2R on lymphocytes in inflammatory diseases are still unidentified. The present study aimed at evaluating the influence of interleukin 1 beta (IL-1 beta) and interleukin 2 (IL-2) on the number and on the dissociation constant (KD) of beta 2R on PBMC in vitro. PBMC from healthy volunteers were incubated with different concentrations of IL-1 beta (10-100 U/ml) or IL-2 (10-50 U/ml) for 1,6,12,24 and 72 hours (h), respectively. Cultures with medium alone served as controls. beta 2R were determined using a radioligand binding assay with 125Iodo-cyanopindolol. The results showed a significant spontaneous decline of beta 2R after 72 h (mean +/- SEM = 2674 +/- 392 binding sites/cell (bs/c) vs. 1131 +/- 149 bs/c P < 0.02). IL-2 at a concentration of 50 U/ml diminished this spontaneous reduction of beta 2R numbers significantly (control: 1439 +/- 139 bs/c vs. IL-2: 1724 +/- 107 bs/c, P < 0.05). However, beta 2R densities did not hold baseline levels and were still significantly lower as compared to preculture values. Incubation with 100 U/ml IL-1 beta for 6 h induced a significant increase of beta 2R densities (control: 1760 +/- 214 bs/c vs. IL-1: 2233 +/- 424 bs/c, P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)