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Keywords:

  • cyclic AMP;
  • allergic asthma;
  • potentiation;
  • cortisol;
  • circannual variation;
  • PBMCs

Background

Dysfunction of the β-adrenoceptor (βAR)/adenylyl cyclase (AC) system can impair the response of different cell types, including lymphocytes. In asthma, impairment of this system as well as changes in cytokine production by lymphocytes have been described. Because the severity of asthma can change over the year, a circannual pattern of the βAR/AC system activity may also exist.

Objectives

We set out to examine the activity of this βAR/AC signal transduction system in peripheral blood mononuclear cells (PBMCs) of allergic asthmatics to asses whether differences existed between seasons. We investigated whether changes were associated with asthma severity and circannual changes in serum cortisol levels.

Methods

During 19 months, 41 allergic asthmatics (mean age 28 years) with nocturnal airway obstruction were enrolled in the study. AC activity was measured by cyclic AMP production. Resting, stimulated and potentiated AC activities and their relationships with clinical parameters, seasonal influences and serum cortisol levels were assessed.

Results

The AC activity in resting, stimulated and potentiated cells varied during the year. AC activity was relatively low in the periods June–August and September–November, and higher in December–February and March–May. Receptor-mediated and potentiated responses expressed as percentage of the resting response were equivalent throughout the year. Serum cortisol levels were positively related to AC activity. No relationships were found between clinical parameters and AC activity or serum cortisol levels.

Conclusions

These results indicate that AC activity in PBMCs of allergic asthmatics shows a seasonal variation. However, seasonal differences in AC activity seems to be unrelated with clinical parameters. Other factors such as serum cortisol levels may have a modulating influence on AC activity. Future studies of AC systems in blood cells of asthmatic patients need to take into account these seasonal influences.