formycins and Immunologic-Deficiency-Syndromes

Topics: Adenosine; Adenosine Deaminase; Blood Platelets; Erythrocytes; Formycins; Guanine; Guanosine; Guanosine Triphosphate; Humans; Immunologic Deficiency Syndromes; Lymphocytes; Platelet Aggregation; Purine Nucleosides; Ribonucleotides; Structure-Activity Relationship

The absence of erythrocytic adenosine deaminase (ADA) or purine nucleoside phosphorylase (PNP) has been associated with severe immunodeficiency disease in children. We have developed a cell culture model to study the possible relationships between purine salvage enzymes and immunologic function using an established T cell lymphosarcoma (S49) and a potent inhibitor of ADA, erythro-9(2-hydroxy-3-nonyl) adenine (EHNA). Wild-type S49 cells are killed by dexamethasone or dbc AMP, and adenosine (5 muM) in the presence of an ADA inhibitor (6 muM EHNA) also prevents the growth of and kills these S49 cells. It has been proposed that adenosine is toxic to lymphoid cells by virtue of its ability to increase the intracellular concentrations of cyclic AMP. We examined the sensitivity of three mutants of S49 cells, with distinctive defects in some component of cyclic AMP metabolism or action, to killing by adenosine and EHNA. All three mutants are resistant to killing by isoproterenol or cholera toxin and two are resistant to dbc AMP itself, but all are sensitive to killing by adenosine and EHNA. Similarly, two dexamethasone-resistant S49 mutants are as sensitive to adenosine and EHNA as are the wildtype cells. We have also simulated the purine nucleoside phosphorylase deficiency in S49 cells by adding inosine and adenosine to the growth medium. In the presence of EHNA or inosine, the toxic effects of adenosine can be partially reversed by addition of (10-20 muM) uridine, an observation suggesting that adenosine is toxic as the result of its inducing pyrimidine starvation.

Topics: Adenine; Adenosine; Adenosine Deaminase; Adenosine Deaminase Inhibitors; Bucladesine; Cell Line; Cell Survival; Cyclic AMP; Dexamethasone; Formycins; Immunologic Deficiency Syndromes; Inosine; Nucleoside Deaminases; Pentosyltransferases; Purine-Nucleoside Phosphorylase; Uridine

Deficiency of erythrocytic and lymphocytic adenosine deaminase (ADA) occurs in some patients with severe combined immunodeficiency disease (SCID). SCID with ADA deficiency is inherited as an autosomal recessive trait. ADA is markedly reduced or undetectable in affected patients (homozygotes), and approximately one-half normal levels are found in individuals heterozygous for ADA deficiency. The metabolism of purine nucleosides was studied in erythrocytes from normal individuals, four ADA-deficiency patients, and two heterozygous individuals. ADA deficiency in intake erythrocytes was confirmed by a very sensitive ammonia-liberation technique. Erythrocytic ADA activity in three heterozygous individuals (0.07,0.08, and 0.14 mumolar units/ml of packed cells) was between that of the four normal controls (0.20-0.37 mumol/ml) and the ADA-deficient patients (no activity). In vitro, adenosine was incorporated principally into IMP in the heterozygous and normal individuals but into the adenosine nucleotides in the ADa-deficient patients. Coformycin (3-beta-D-ribofuranosyl-6,7,8-trihydroimidazo[4,5-4] [1,3] diazepin-8 (R)-ol), a potent inhibitor of ADA, made possible incorporation of adenosine nucleotides in the ADA-deficient patients...

Topics: Adenosine Deaminase; Adenosine Deaminase Inhibitors; Adenosine Diphosphate; Adenosine Triphosphate; Azepines; Child, Preschool; Erythrocytes; Female; Formycins; Glycolysis; Guanosine; Humans; Immunologic Deficiency Syndromes; Infant; Inosine Monophosphate; Inosine Nucleotides; Male; Nucleoside Deaminases; Purine Nucleosides; Ribonucleosides; Thioguanine