Adrenaline upregulates monocyte L-selectin in vitro.
OBJECTIVE
Although surface adhesion molecules mediate leucocyte-endothelial interactions at sites of inflammation, relatively little is known of the factors which increase the expression of L-selectin in circulating leucocytes. The expression of leucocyte L-selectin increases during acute stress events such as injury and is temporally related to an early neuroendocrine response. This study investigates whether adrenaline increases the expression of L-selectin on monocytes, neutrophils and lymphocytes in vitro and whether these effects are mediated via beta-adrenoceptors.


METHODS
A total of 20 ml of blood was withdrawn from 28 healthy volunteers (21 males) with a mean age of 29 years (range 23-67 years). Adrenaline at physiological doses mimicking trauma (0-200 nmol/l) was added to whole blood prior to immunofluorescent staining and analysis by flow cytometry. Propranolol (50 microl of 2 x 10(-5) M) was also added to separate tubes prior to incubation with adrenaline. Saline (40 microl 0.9% solution) was used as a control. Expression is described firstly as percentage of cells expressing L-selectin and secondly as average intensity (mean channel fluorescence, mcf) per cell expressing CD62L. Summary measures were used to analyse the data.


RESULTS
A significant increase in both the percentage of monocytes expressing L-selectin and mean channel fluorescence of L-selectin was evident with adrenaline in vitro (P < 0.0001). Maximal increases occurred at 100 nmol/l adrenaline when a 9% increase in the percentage of monocytes expressing L-selectin and a 23% increase in mean channel fluorescence were observed. These effects were both blocked by propranolol (P < 0.0001). No significant differences were observed for neutrophils or lymphocytes except for a slight increase in the percent neutrophils expressing L-selectin, and a small decreasing trend in percent lymphocytes expressing L-selectin.


CONCLUSIONS
Adrenaline upregulates the surface expression of L-selectin on monocytes in vitro, an effect which is partially mediated by beta-adrenoceptors. As monocytes initiate early aspects of the inflammatory response, these findings suggest that beta-blockade may have an inhibitory role for certain aspects of leucocyte trafficking.
Rainer
T H
TH
Accident and Emergency Medicine Academic Unit, The Chinese University of Hong Kong, Cancer Centre, Prince of Wales Hospital, Shatin, NT. rainer1091@cuhk.edu.hk
Lam
N
N
Cocks
R A
RA
D000328:Adult; D004837:Epinephrine / Q000494:pharmacology* / Q000502:physiology; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D066298:In Vitro Techniques; D019041:L-Selectin / Q000378:metabolism*; D008214:Lymphocytes / Q000378:metabolism; D008297:Male; D009000:Monocytes / Q000378:metabolism*; D009504:Neutrophils / Q000378:metabolism; D011433:Propranolol / Q000494:pharmacology; D011943:Receptors, Adrenergic, beta / Q000502:physiology; D015854:Up-Regulation
D011943:Receptors, Adrenergic, beta; D019041:L-Selectin; D011433:Propranolol; D004837:Epinephrine