SEASONAL-VARIATIONS IN CYCLIC-AMP PRODUCTION BY PERIPHERAL-BLOOD MONONUCLEAR-CELLS IN ALLERGIC ASTHMATICS

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.