We determined characteristics of beta2-adrenergic receptors (beta2R) on peripheral blood mononuclear cells (PBMC) and cytokine production after mitogenic stimulation and coincubation with catecholamines. PBMCs were stimulated with interleukin-2 (IL-2), tetanus toxoid (TT), anti-CD3 antibody, or phytohemagglutinin (PHA). The cytokines interferon-gamma (IFN-gamma), IL-4, and IL-6 were determined by ELISA following coincubation with high-dose (10(-5) M) and low-dose (10(-9) M) epinephrine (EPI) and norepinephrine (NE). Intracellular IFN-gamma and IL-4 were studied by FACS analysis. The beta2R density was investigated using a radioligand binding assay. The stimuli induced various cytokine profiles in PBMCs. Synthesis of IFN-gamma was induced by all mitogens and could be suppressed by catecholamines (26%-85% reduction). In PHA-stimulated PBMCs, IL-4 synthesis was decreased by high-dose catecholamines (24%-28% reduction). Adding a beta-blocking agent attenuated most catecholamine effects. A highly significant negative correlation between the density of beta2R with IFN-gamma and IL-6 levels of PHA-activated PBMCs (r = -0.88 to -0.96, p < 0.01-< 0.001) was observed. The results indicate that the density of beta2R on PBMC plays a role in mediating the differential catecholamine effects on cytokine production of PBMC. Furthermore, changes in cytokine expression induced by catecholamines favor Th2 responses.
There was a highly significant distortion between patients with RA and controls in the distribution of beta2AR polymorphisms at codon 16, contributing (together with the HLA-DR alleles) to the genetic background of RA.
The systemic CD4+ T cell compartment in patients with rheumatoid arthritis (RA) is characterized by TCR repertoire contraction, shortened telomere lengths, and decreased numbers of recent thymic emigrants, suggesting a disturbed CD4+ T cell homeostasis. In mice, homeostatic proliferation of peripheral CD4+ T cells is regulated by TCR interaction with self peptide-MHC complexes (pMHC) and can be reproduced in vitro. We have established an ex vivo model of homeostatic proliferation, in which self-replication of human CD4+ T cells is induced by cell-cell contact with autologous monocytes. In healthy individuals, blockade of TCR-pMHC class II contact resulted in decreased CD4+ T cell division. In contrast, homeostatic proliferation in RA patients was not inhibited by pMHC blockade, but increased during the initial culture period. The anti-TNF-α Ab cA2 inhibited homeostasis-driven ex vivo proliferation in healthy controls and in RA patients. In addition, treatment of RA patients with infliximab decreased the ex vivo rate of homeostatic proliferation of CD4+ T cells. Our results suggest a disturbed regulation of CD4+ T cell homeostasis leading to the repertoire aberrations reported in RA. Membrane-anchored TNF-α appears to be a cell-cell contact-dependent stimulus of homeostatic proliferation of CD4+ T cells, possibly favoring self-replication of autoreactive CD4+ T cells in patients with RA.
Objective-To investigate further the influence of the autonomic nervous system on chronic rheumatic diseases. Methods-The density and aYnity of 2 adrenergic receptors ( 2R) on CD19+ lymphocytes in patients with rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), and systemic sclerosis (SSc), as well as intracellular cAMP levels in patients with RA and SLE, were determined. Human peripheral blood mononuclear cells were separated from venous blood of patients and healthy controls by Ficoll-Hypaque density centrifugation. CD19+ lymphocytes were purified by magnetic cell sorting, and 2R were determined by a radioligand binding assay with [ 125 I]iodocyanopindolol. Intracellular cAMP levels and 2R agonist induced cell death were measured by a radioimmunoassay and flow cytometry using annexin-V binding, respectively. Systemic disease activity of the patients was evaluated using multifactorial scoring systems. Results-The density of 2R on peripheral CD19+ lymphocytes was significantly decreased in patients with RA, SLE, and SSc compared with healthy controls. In patients with RA and SSc 2R density was negatively correlated with systemic disease activity. Furthermore, although basal intracellular cAMP levels were raised in patients with RA and SLE, the increase of cAMP upon stimulation of 2R was significantly reduced in these patients compared with control subjects. Preliminary data suggest that 2R agonist induced cell death is diminished in patients with RA exhibiting decreased 2R densities. Conclusions-The results of this study show a reduction of 2R densities on B lymphocytes mirrored by an impaired intracellular cAMP generation in patients with chronic rheumatic diseases, indicating a decreased influence of the autonomic nervous system on B cells in these conditions.
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