Y. Hoekstra et al., SEASONAL-VARIATIONS IN CYCLIC-AMP PRODUCTION BY PERIPHERAL-BLOOD MONONUCLEAR-CELLS IN ALLERGIC ASTHMATICS, Clinical and experimental allergy, 28(3), 1998, pp. 271-277
Background Dysfunction of the beta-adrenoceptor (beta AR)/adenylyl cyc
lase (AC) system can impair the response of different cell types, incl
uding lymphocytes. In asthma, impairment of this system as well as cha
nges in cytokine production by lymphocytes have been described. Becaus
e the severity of asthma can change over the year, a circannual patter
n of the beta AR/AC system activity may also exist. Objectives We set
out to examine the activity of this beta AR/AC signal transduction sys
tem in peripheral blood mononuclear cells (PBMCs) of allergic asthmati
cs to asses whether differences existed between seasons. We investigat
ed whether changes were associated with asthma severity and circannual
changes in serum cortisol levels. Methods During 19 months, 41 allerg
ic asthmatics (mean age 28 years) with nocturnal airway obstruction we
re enrolled in the study. AC activity was measured by cyclic AMP produ
ction. Resting, stimulated and potentiated AC activities and their rel
ationships with clinical parameters, seasonal influences and serum cor
tisol levels were assessed. Results The AC activity in resting, stimul
ated and potentiated cells varied during the year. AC activity was rel
atively low in the periods June-August and September-November, and hig
her in December-February and March-May. Receptor-mediated and potentia
ted responses expressed as percentage of the resting response were equ
ivalent throughout the year. Serum cortisol levels were positively rel
ated to AC activity. No relationships were found between clinical para
meters and AC activity or serum cortisol levels. Conclusions These res
ults indicate that AC activity in PBMCs of allergic asthmatics shows a
seasonal variation. However, seasonal differences in AC activity seem
s to be unrelated with clinical parameters. Other factors such as seru
m cortisol levels may have a modulating influence on AC activity. Futu
re studies of AC systems in blood cells of asthmatic patients need to
take into account these seasonal influences.