β‐Adrenergic receptor density and function of peripheral blood mononuclear cells are increased in multiple sclerosis: A regulatory role for cortisol and interleukin‐1

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Abstract
An increased density of β‐adrenergic receptors was demonstrated on peripheral blood mononuclear cells (PMMCs) from patients with progressive or replapsing‐remitting multiple sclerosis (MS). The same observation was made in patients with chronic active rheumatoid arthritis, but not in those with myasthenia gravis. The affinity of the receptors was within the normal range in all tested groups of patients and there was a positive correlation between density and function as determined by intracellular cyclic AMP production after stimulation with isoproterenol. A putative link between inflammatory processes and the functional upregulation of β‐adrenergic receptors on PBMCs was tested by in vitro studies with the soluble mediators interleukin‐1 and hydrocortisone. A functional upregulation of β‐adrenergic receptors was observed when PBMCs from normal control subjects were cultured in the presence of either mediator, whereas the already upregulated receptor density on PBMCs from patients with MS remained unchanged. Whether this represents a recovery mechanism to inflammation in MS or a blunting of homeostatic immunoregulatory mechanisms requires further investigation.