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beta-Adrenergic regulation of proinflammatory cytokines in humans
V Mohamed-Ali1, K Bulmer, D Clarke
1Department of Medicine, University College London Medical School, Whittington Hospital, UK. rmhauma@ucl.ac.uk
Objectives:
To investigate the effects of beta-adrenergic stimulation on IL-6 secretion in humans, and to determine the potential contribution to this response of adipocytes and peripheral blood cells (PBC).
Design:
Experimental study in 8 human volunteers, and in vitro studies on murine adipocyte cell-line, 3T3.L1 and 3T3.F442A, and human PBC.
Measurements:
Plasma IL-6 and TNFalpha responses to isoprenaline infusion. Cytokine secretion from differentiated adipocyte cell-lines and PBC in response to isoprenaline.
Results:
Plasma IL-6 levels increased ninefold (median) by 180 min (baseline median 0.51 [interquartile range 0.47-1.4] vs 180 mins 4.53 [2.58-5.69] pg ml(-1), P=0.01). One hour after infusion, IL-6 levels (2.9 [1.27-3.98]) were lower than at 180 min (P=0.05), but higher than baseline (P=0.01). TNFalpha levels were unchanged. Differentiated adipocytes incubated in isoprenaline (0-0.1 microM) released significantly increased amounts of IL-6 whereas no response was elicited from PBC.
Conclusions:
The induction of IL-6 observed in vivo may be attributed to the beta-adrenergic stimulation of IL-6 release specifically from adipocytes, as opposed to circulating blood cells.