The role of adenosine receptors in the action of theophylline on human peripheral blood mononuclear cells from healthy and asthmatic subjects

1 The aim of the present study was to investigate the role of adenosine A2b receptors in the antiproliferative action of theophylline in hut-nan peripheral blood mononuclear cells (HPBMC) from healthy and asthmatic subjects. 2 Theophylline significantly inhibited PHA-induced proliferation of HPBMC from both healthy and asthmatic donors but only at relatively high concentrations at 1 mM (P0.05; n=6). 3 Adenosine deaminase (2 u ml(-1)). which metabolizes adenosine, had no significant effect on PHA-induced HPBMC proliferation over a range of concentrations (0-8 mu g ml(-1)) in cells from either healthy or asthmatic subjects. 4 The adenosine receptor agonists N-6-cyclopentyladenosine (CPA, Al-selective) and 5'-N-ethylcarboxamidoadenosine (NECA, A1/A2) produced a small but significant inhibition of PHA-induced proliferation of HPBMC from healthy and asthmatic subjects (10 mu M, P0.05, n=6). 5 The adenosine receptor antagonist alloxazine (A2b-selective) had no significant effect, while 8(3-chlorostyryl)caffeine,(CSC, A2a-selective) significantly inhibited PHA-induced proliferation of HPBMC from both groups (P