The adenosine/neutrophil paradox resolved: human neutrophils possess both A1 and A2 receptors that promote chemotaxis and inhibit O2 generation, respectively.

Occupancy of specific receptors on neutrophils by adenosine or its analogues diminishes the stimulated release of toxic oxygen metabolites from neutrophils, while paradoxically promoting chemotaxis. We now report evidence that two distinct adeno- sine receptors are found on neutrophils (presumably the Al and A2 receptors of other cell types). These adenosine receptors modulate chemotaxis and 02 generation, respectively. N6-Cyclopentyladenosine (CPA), a selective A, agonist, promoted neutrophil chemotaxis to the chemoattractant FMLP as well as or better than 5'N-ethylcarboxamidoadenosine (NECA). In contrast, CPA did not inhibit O2 generation stimulated by FMLP. Pertussis toxin completely abolished promotion of chemotaxis by CPA but enhanced inhibition by NECA of 02 generation. Disruption of microtubules by colchicine or vin- blastine also abrogated the enhancement by NECA of chemo- taxis whereas these agents did not markedly interfere with inhibition by NECA of 2 generation. FMLP receptors, once they have bound ligand, shift to a high affinity state and be- come associated with the cytoskeleton. NECA significantly increased association of I3HIFMLP with cytoskeletal prepara- tions as it inhibited 2.-Disruption of microtubules did not prevent NECA from increasing association of PHIFMLP with cytoskeletal preparations. Additionally, CPA (Al agonist) did not increase binding of IHIFMLP to the cytoskeleton as well as NECA (A2 agonist). These studies indicate that occupancy of one class of adenosine receptors (Al) promotes chemotaxis by a mechanism requiring intact microtubules and G proteins whereas engagement of a second class of receptors (A2) in- hibits 0generation. Signalling via A2 receptors is indepen- dent of microtubules, insensitive to pertussis toxin and is asso- ciated with binding of [HjFMLP to cytoskeletal preparations. (J. Clin. Invest. 1990 Invest. . 85:1150Invest. -1157.) adenosine * adenosine receptor* neutrophil * cytoskeleton * chemotaxis 1. Abbreviations used in this paper: CGS-2 1680, 2-para-2-carboxyethylphenylamino-5'N-ethylcarboxamidoadenosine; CPA, N6-cyclopen- tyladenosine; CV-1 808, 2-phenylaminoadenosine; EC", the concen- tration at which half-maximal enhancement occurs; IC50, the concen- tration at which half-maximal inhibition occurs; NECA, 5'N-ethylcarboxamidoadenosine; O2, superoxide anion; PIA, N6- phenylisopropyladenosine.