Patterns of cyclic nucleotides in normal and leukaemic human leucocytes

Duodenal mucosa and extracellular cyclic nucleotide pattern in coeliac disease

This study measured the values of cyclic nucleotides and adenylate and guanylate cyclase activities in duodenal mucosa homogenates to verify if they played a part in coeliac disease. Nine controls, 13 patients who did not receive treatment and nine patients who received treatment were studied. Cyclase activity assays were performed under basal conditions and in the presence of gliadin derived peptides. Duodenal mucosa cyclic nucleotide values and adenylate cyclase activity were significantly higher in patients who did not receive treatment than in those who did and in controls, whereas guanylate cyclase activity was similar in all groups. Gliadin derived peptides did not affect guanylate cyclase activity, but significantly increased adenylate cyclase activity in homogenates from patients who did not receive treatment. As extracellular cyclic nucleotide concentrations could reflect changes in their intracellular metabolism, plasma and urine cyclic nucleotide values were also measured in 25 controls and in 55 patients studied at different stages of their disease. Extracellular cyclic nucleotides were considerably high in patients who were not healed and became normal after about one year of treatment. These data suggest that cyclic nucleotides may participate in the pathophysiological processes of coeliac disease.

Reduced responsiveness of adenylate cyclase to forskolin in human lymphoma cells

The beta 2-adrenergic transmembrane signal transduction was investigated in malignant B-cells from 15 patients with low grade non-Hodgkin's lymphoma as compared with normal lymphocytes of seven healthy adults. The number of beta 2-adrenoceptors and the response of adenylate cyclase (AC) to isoproterenol were slightly decreased in lymphoma cells. The responsiveness of AC to forskolin was 8-fold lower in lymphoma cells, whereas the response to cholera toxin showed no difference. These findings demonstrate an impairment of the beta 2-adrenergic signal transduction in low grade lymphoma cells that particularly affects the function of AC. The comparison with forskolin resistant mutants of an adrenocortical tumor cell line, Y1 (Schimmer et al., J Biol Chem 262: 15521-15526, 1987), suggests that the availability of functional active alpha subunits of stimulatory G proteins (Gs) might be reduced in human B-cell lymphoma, although other mechanisms known to inhibit the AC activity might be involved.

Plasma cyclic nucleotide levels in patients with refractory anaemia with excess of blasts

To verify the clinical usefulness of extracellular cyclic nucleotide determinations as tumour markers in preneoplastic syndromes, plasma cyclic AMP (cAMP) and cyclic GMP (cGMP) levels were monitored in 47 patients with refractory anaemia with excess of blasts (35 RAEB and 12 RAEBt), 20 of whom progressed to acute leukaemia during the observation period. The control group consisted of 45 healthy subjects matched for age and sex. In all groups of patients plasma cAMP levels were within the normal range, whereas plasma cGMP levels were significantly higher than those of normal subjects in both RAEB and RAEBt patients, and increased further when progression to acute leukaemia occurred. These data suggest that serial determinations of plasma cGMP may be useful to monitor the progression of the disease, though there is no evidence that cGMP values at diagnosis may have a prognostic significance.

Effect of high doses of somatostatin on adenylate cyclase activity in peripheral mononuclear leukocytes from normal subjects and from acute leukemia patients

In normal lymphocytes somatostatin non-competitively inhibited basal (ID50 5 x 10(-4) M) and isoproterenol- and forskolin-stimulated adenylate cyclase activity (Ac). In acute leukemia blasts, non-responsive to isoproterenol, forskolin, which activates the catalytic subunit, stimulated and somatostatin inhibited Ac, thus indicating the leukemic enzyme, though defective, retains the inhibitory pathway and catalyst function.

Plasma cyclic nucleotide levels in patients with homozygous beta-thalassaemia

To investigate the possibility that a proliferative non-neoplastic process influences extracellular cyclic nucleotide concentrations, we measured plasma cyclic AMP and cyclic GMP levels in 38 patients with homozygous beta-thalassaemia. This group consisted of 20 patients with thalassaemia major transfused regularly (mean pre transfusion Hb levels, 11 g/dl), and 18 patients with thalassaemia intermedia who did not require regular blood transfusion (mean Hb levels, 8.7 g/dl). In the patient group, plasma cyclic AMP levels were similar to those of 37 normal subjects matched for age and sex, whereas plasma cyclic GMP levels were markedly higher. Moreover, in the thalassaemic patients there was a significant negative correlation between plasma cyclic GMP levels and haemoglobin concentrations, suggesting that their marked erythroid hyperplasia may play a role in determining alterations in extracellular cyclic GMP levels.

Plasma and urine cyclic nucleotide levels in patients with neoplastic diseases

Plasma and/or urine cyclic adenosine 3',5'-monophosphate (cAMP) and cyclic guanosine 3',5'-monophosphate (cGMP) levels were measured in 67 normal subjects, 55 patients with nonneoplastic diseases, and 324 patients with ten different types of cancer. There were no significant differences in plasma and urine cyclic nucleotide levels between normal subjects and patients with non-neoplastic diseases. In untreated cancer patients, plasma and urine cAMP levels were similar to those of normal subjects, whereas plasma and urine cGMP levels were markedly higher. This pattern was common to all the cancer groups studied. Chemotherapy per se did not seem to influence cyclic nucleotide levels in cancer patients. However, plasma and urine cGMP levels normalized in all patients who attained complete remission. Moreover, in acute leukemia patients who relapsed, plasma cGMP levels increased significantly with respect to the complete remission values, thus suggesting that this parameter may be useful in monitoring the response of cancer patients to treatment.

Cyclic AMP-dependent and -independent protein kinases and protein phosphorylation in human promyelocytic leukemia (HL60) cells induced to differentiate by retinoic acid

The human leukemia cell line HL60 which resembles promyelocytes can be induced to differentiate to cells displaying features of the mature myeloid phenotype by a variety of agents including retinoic acid (RA) and agents that elevate intracellular adenosine 3:5 cyclic monophosphate (cyclic AMP) levels, e.g., 8-bromo-cyclic adenosine 3:5 monophosphate (8-Br-cyclic AMP), cholera toxin. Since most, if not all the effects of cyclic AMP, are mediated by adenosine 3:5 cyclic monophosphate-dependent protein kinase (cyclic AMP-dPK), we investigated the role of cyclic AMP-dPK and adenosine 3:5 cyclic monophosphate-independent protein kinase (cyclic AMP-iPK) in the induced differentiation of HL60 cells. Marked stimulation of cyclic AMP-dPK and cyclic AMP-iPK appears to be intimately involved with and specific for HL60 myeloid differentiation as evidenced by: (1) Stimulation of cyclic AMP-dPK and cyclic AMP-iPK early during HL60 myeloid differentiation and prior to phenotypic changes. (2) RA and dimethylformamide (DMF), agents that induce differentiation along the myeloid pathway, cause a marked increase in the type l cytosolic cyclic AMP-dPK and cyclic AMP-iPK (protamine kinase) while no such increases are noted in cells treated with 12-0-tetradecanoyl-phorbol-13-acetate (TPA) which induces differentiation along the monocyte/macrophage pathway. (3) Both native polyacrylamide gel electrophoresis as well as photoaffinity labeling with 8-azido-cyclic AMP demonstrate marked increases in type l cyclic AMP-dPK in the cytosols of cells exposed to agents that induce myeloid differentiation but no increase in TPA-differentiated cells. (4) The appearance and disappearance of specific cyclic AMP-dependent and -independent protein phosphorylations are associated with the induced myeloid differentiated state.

Differences in beta-adrenergic receptor density and adenylate cyclase activity between normal and leukaemic leukocytes

An identical class of high-affinity binding sites for the 125I-labelled beta-adrenergic antagonist hydroxybenzylpindolol, was identified on intact human normal and leukaemic peripheral blood leukocytes. On normal unfractionated lymphocytes, polymorphonuclear leukocytes, and monocytes, receptor density did not differ significantly (1200-1400 receptors per cell; P greater than 0.3), but it was higher on B- than on T-lymphocytes (P less than 0.05). In leukaemia, monocytic blast cells expressed highest receptor numbers, whereas very low receptor density was seen on the pathologic B-cells from chronic lymphocytic leukaemia. Among normal leukocytes, adenylate cyclase activation by hormones (isoproterenol, prostaglandin E1, histamine) and sodium fluoride was strongest in plasma membranes from monocytes, but very weak in polymorphonuclear leukocytes either due to uncoupling of hormone receptors from adenylate cyclase or to low catalytic activity. In T-cells, enzyme activity was significantly lower than in B-cells. Loss of adenylate cyclase sensitivity to hormones and fluoride occurred in leukaemic cells from chronic and acute lymphocytic leukaemia.