Attenuation of ecto-5'-nucleotidase activity and adenosine release in activated human polymorphonuclear leukocytes.

Abstract

Listen

Translate article

To examine whether activation of polymorphonuclear leukocytes attenuates release of adenosine through attenuation of their own ecto-5'-nucleotidase activity, human polymorphonuclear leukocytes were incubated with and without exposure to either N-formyl-methionyl-leucyl-phenylalanine (FMLP) or complement C5a. Ecto-5'-nucleotidase activity of polymorphonuclear leukocytes was attenuated by both FMLP and complement C5a (22.7 +/- 3.6 vs 9.7 +/- 2.6 nmol/min per 10(7) cells at 10(-6) M FMLP, P < .05; 21.5 +/- 2.2 vs 10.2 +/- 1.2 nmol/min per 10(7) cells at 5 x 10(-7) g/mL complement C5a, P < .001), whereas cytosolic 5'-nucleotidase activity was not affected by either FMLP or complement C5a. These reductions of ecto-5'-nucleotidase activity that were caused by both FMLP and complement C5a were dose and time dependent and were inhibited by superoxide dismutase. Desferrioxamine did not inhibit the decreases in ecto-5'-nucleotidase. In accordance with the decreases in ecto-5'-nucleotidase activity, release of adenosine was attenuated in the FMLP-pretreated and complement C5a-pretreated polymorphonuclear leukocytes, which were restored by concomitant administration of superoxide dismutase. The viability of FMLP-pretreated and complement C5a-pretreated polymorphonuclear leukocytes was markedly decreased compared with the untreated group after 60 minutes of hypoxia followed by 60 minutes of reoxygenation. Thus, we conclude that: (1) activation of polymorphonuclear leukocytes attenuates their own ecto-5'-nucleotidase activity and thereby reduces adenosine release, (2) reduction of ecto-5'-nucleotidase activity is attributable to generated superoxide anion in polymorphonuclear leukocytes, and (3) viability of polymorphonuclear leukocytes after hypoxia and reoxygenation largely depends on the extents of decreases in ecto-5'-nucleotidase activity.