Purine catabolism in polymorphonuclear neutrophils. Phorbol myristate acetate-induced accumulation of adenosine owing to inactivation of extracellularly released adenosine deaminase.

Abstract

Since physiological concentrations (0.1-1 pM) of adenosine influence the functions of human polymorphonuclear neutrophils (PMNs), we investigated the metabolism of adenosine in suspensions of stimulated and unstimulated PMNs. Stimulation with phorbol myristate acetate (PMA, 1 MM), but not by zymosan (0.5 mg/ml) or N-formyl-methionyl-leucyl-phenylalanine (fMLP, 1 MM), provoked an accumulation of endogenous adenosine at a rate of 23±1.0 amol/cell per minute. A similar accumulation was observed with both unstimulated and stimulated PMNs after the addition of deoxycoformycin (dCF, 1-100 MM), an inhibitor of adenosine deaminase. Exogenous adenosine (10 MM) was deaminated at a rate of 9.8±3.7 amol/ cell per minute in control or zymosan or fMLP-stimulated PMN suspensions. This deamination was nearly completely suppressed when the PMNs had been stimulated with PMA. In contrast, the activity of adenosine deaminase in PMN lysates (231±72 amol/cell per minute) was not modified by PMA stimulation. a,#-Methyleneadenosine 5'-diphosphate (AMPCP, 2.5 mM), an inhibitor of membranous ecto-5'-nucleotidase, profoundly inhibited endogenous adenosine accumulation under all conditions. PMA stimulation also provoked an inactivation of extracellular adenosine d purine nucleoside phosphorylase, and lactate dehydrogenase in PMN suspensions. We concluded that PMNs, even when not stimulated, continuously produce adenosine by dephosphorylation of extracellularly released adenylates; and that stimulation of PMNs by PMA causes adenosine accumulation owing to the inactivation of adenosine deaminase released by broken cells. (J. Clin. Invest. 1991. 87:305-312.)

Inhibition and prevention of monosodium urate monohydrate crystal–induced acute inflammation in vivo by transforming growth factor β1

“…We used the subcutaneous air pouch model described by Edwards et al (26). This model represents a convenient system that shares striking similarities with the synovial membrane, as demonstrated by previous studies that provided both a model of the synovial cavity (26) and an in vivo model for acute inflammation (27). Preliminary results of other studies have suggested that cytokines and growth factors such as TGFP (28,29) are secreted into the air pouch membrane, providing further evidence of the usefulness of this model as a surrogate for the synovial cavity.…”

Impairment of tubuloglomerular feedback regulation of GFR in ecto-5′-nucleotidase/CD73–deficient mice

“…Although e-5′NT/CD73 is believed to have a number of secondary functions (14,15), there is general agreement that the major role of the enzyme consists of converting extracellular 5′-AMP to adenosine. Dependence of tissue adenosine levels on a functional e-5′NT/CD73 enzyme is supported by studies in which inhibition of the enzyme was found to significantly reduce adenosine concentrations (16,17). Thus, it would seem likely that failure to produce appropriate amounts of adenosine in response to an increase in luminal NaCl is the underlying reason for the altered tubuloglomerular feedback responsiveness in e-5′NT/CD73 KO mice.…”

“…We acknowledge the possibility of the alternative explanation that the absence of e-5′NT/CD73 activity may lead to greatly increased ATP concentrations and that this may cause P2 receptor desensitization and subsequent attenuation of tubuloglomerular feedback responses. An increase in extracellular ATP concentration in association with an inhibition of e-5′NT/CD73 has been reported in isolated neutrophils (17). It is not clear, however, that such an effect occurs in a complex tissue in view of the abundance of alternative extracellular ATP breakdown pathways in the form of multiple ecto-ATP diphosphohydrolases, ecto-phosphodiesterase/pyrophosphatases, and alkaline phosphatase (18).…”

Platelet aggregation induced by the endoperoxide analogue U46619 is inhibited by polymorphonuclear leukocyte ADPase activity.

“…The inhibitory activity of PMNs (10 7 /mL) on platelet aggregation was prevented by the ecto-5'-nucleotidase inhibitor a,/3-methyleneadenosine 5'-diphosphate used at a concentration reported to inhibit ectoADPase activity as well. 27 Moreover, PMN inhibition was not prevented by adenosine deaminase used at concentrations (0.3-1.25 /xg/mL) that did not in themselves affect platelet aggregation induced by U46619. In the presence of PMNs, aggregated platelets were 12±2% and 18±2% in the absence or presence of adenosine deaminase, respectively (mean±SEM of three separate experiments).…”

“…24 -26 To characterize the nature of the inhibitory activity, we performed a series of experiments with specific inhibitors of ecto-ADPase, 10 5'-nucleotidase, 27 and phosphatase activity. 28 The effect of 100 ^mol/L )3,ymethyleneadenosine 5'-triphosphate, 2.5 mmol/L a,J3-methyleneadenosine 5'-diphosphate, and 100 jtmol/L levamisole was tested on U46619-induced platelet aggregation in platelet and platelet-PMN suspensions ( Table 1).…”