Theophylline inhibits the differentiation of human monocyte into dendritic cell potentially via adenosine receptor antagonism.
BACKGROUND
Theophylline has an anti-inflammatory action that may account for its clinical effectiveness in the reduction of inflammatory cells in the airways. Dendritic cells (DCs) are professional antigen-presenting cells, capable of priming naïve T cells, and play key roles in the activation of immune responses in asthma.


OBJECTIVE
The purpose of this study was to investigate the effects of theophylline on human monocyte differentiation into DCs and whether this involved antagonism of adenosine receptors.


METHODS
Peripheral human blood monocytes were cultured in the presence of granulocyte/macrophage-colony stimulating factor and IL-4 to induce DC differentiation. The cells were incubated with theophylline, KF17837 (a selective A2a receptor antagonist) and enprofylline (A2b receptor antagonist) and co-incubated with selective adenosine A1 and A2a receptor agonists, a phosphodiesterase inhibitor (rolipram) and adenosine deaminase (ADA) to determine their effects on DC differentiation. In addition, depletion of adenosine receptors by small interfering RNA (siRNA) was also examined.


RESULTS
Monocytes differentiated into myeloid DCs in the culture system. The number of DCs was remarkably reduced by 60-70% when theophylline was administered at a therapeutic concentration. This effect was concentration-dependently exacerbated, was partly mediated by cellular apoptosis and was effectively reversed by the addition of the A1 agonists [2-chloro-N(6)-cyclopentyladenosin, N(6)-cyclohexyladenosine, and N-ethylcarboxamidoadenosine (NECA)] or the A2a agonist (CGS-21680, NECA). The depletion of the adenosine A1 receptor by siRNA and addition of ADA remarkably reduced DC differentiation. Meanwhile, both enprofylline and rolipram had little effect.


CONCLUSIONS
Our findings suggest that the adenosine A1 (and possibly coordinated with A2a) receptors contribute to DC differentiation and survival. These findings provide further evidence that theophylline has an anti-inflammatory action in bronchial asthma.
Yasui
K
K
Department of Pediatrics, Dentistry and Pharmaceutical Sciences, Okayama University Graduate School of Medicine, Okayama, Japan. k-yasui@md.okayama-u.ac.jp
Kondo
Y
Y
Wada
T
T
Yashiro
M
M
Tsuge
M
M
Morishima
T
T
D000241:Adenosine / Q000031:analogs & derivatives / Q000494:pharmacology; D058907:Adenosine A1 Receptor Agonists; D058908:Adenosine A2 Receptor Agonists; D058917:Adenosine A2 Receptor Antagonists; D000243:Adenosine Deaminase / Q000494:pharmacology; D019830:Adenosine-5'-(N-ethylcarboxamide) / Q000494:pharmacology; D000328:Adult; D017209:Apoptosis / Q000187:drug effects; D039521:CD11c Antigen / Q000378:metabolism; D053148:Caspase 3 / Q000378:metabolism; D002454:Cell Differentiation / Q000187:drug effects*; D003713:Dendritic Cells / Q000166:cytology* / Q000378:metabolism; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000494:pharmacology; D006684:HLA-DR Antigens / Q000378:metabolism; D006801:Humans; D015847:Interleukin-4 / Q000494:pharmacology; D008297:Male; D009000:Monocytes / Q000166:cytology* / Q000187:drug effects; D010627:Phenethylamines / Q000494:pharmacology; D058906:Purinergic P1 Receptor Agonists; D058915:Purinergic P1 Receptor Antagonists; D034741:RNA, Small Interfering / Q000235:genetics; D043682:Receptor, Adenosine A1 / Q000235:genetics; D018047:Receptors, Purinergic P1 / Q000502:physiology; D011994:Recombinant Proteins; D020889:Rolipram / Q000494:pharmacology; D013806:Theophylline / Q000494:pharmacology*; D014970:Xanthines / Q000494:pharmacology
D058907:Adenosine A1 Receptor Agonists; D058908:Adenosine A2 Receptor Agonists; D058917:Adenosine A2 Receptor Antagonists; D039521:CD11c Antigen; D006684:HLA-DR Antigens; C508598:IL4 protein, human; D010627:Phenethylamines; D058906:Purinergic P1 Receptor Agonists; D058915:Purinergic P1 Receptor Antagonists; D034741:RNA, Small Interfering; D043682:Receptor, Adenosine A1; D018047:Receptors, Purinergic P1; D011994:Recombinant Proteins; D014970:Xanthines; C061282:2-(4-(2-carboxyethyl)phenethylamino)-5'-N-ethylcarboxamidoadenosine; C081198:KF 17837; D015847:Interleukin-4; D019830:Adenosine-5'-(N-ethylcarboxamide); C027513:N(6)-cyclohexyladenosine; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D013806:Theophylline; C034347:enprofylline; D053148:Caspase 3; D000243:Adenosine Deaminase; D020889:Rolipram; D000241:Adenosine