Activity of cyclic AMP phosphodiesterase and methyltransferases in leukocyte membranes from allergic patients

Cyclic nucleotide phosphodiesterases and methyltransferases in purified lymphocytes, monocytes and polymorphonuclear leucocytes from healthy donors and asthmatic patients

Cyclic nucleotide phosphodiesterase and phospholipid N-methyl-transferase activities were simultaneously measured in purified polymorphonuclear cell-, mononuclear cell-, lymphocyte- and monocyte-homogenates from control subjects, from patients with atopic asthma and from patients with non-atopic asthma. Whereas cyclic AMP and cyclic GMP phosphodiesterase activities were found to be about 10-fold lower in polymorphonuclear than in mononuclear cells, phospholipid N-methyltransferase proved to be rather similar in each cell type from control donors. Cyclic AMP phosphodiesterase and phospholipid N-methyltransferase were significantly decreased in polymorphonuclear cells and monocytes from asthmatic patients compared with the control group while cyclic GMP phosphodiesterase was significantly impaired only in the monocyte subpopulation.

Methyltransferase and phospholipase A2 activity in the cell membrane of neutrophils and lymphocytes from patients with Behçet's disease, systemic lupus erythematosus, and rheumatoid arthritis

Phospholipid methylation and phospholipase A2 activation in the membrane of neutrophils and lymphocytes, which participate in the induction of cell activation, were assessed in patients with Behçet's disease, systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA). [3H-methyl] incorporation and phospholipase A2 activity of neutrophils from active cases of Behçet's disease and RA were significantly increased compared with normal controls. In lymphocytes from the patients with active Behçet's disease and RA, a significant increase in methyltransferase activity and a marked enhancement of phospholipase activity were found. A modest increase in these two membrane phospholipid enzyme activities was observed in lymphocytes of patients with active SLE. In addition, these enzyme activities were significantly enhanced in normal leukocytes preincubated with serum from patients with active SLE and malignant RA. The potentiated functions of neutrophils and lymphocyte abnormalities in the patients tested thus seem to be at least partly due to an increase in these enzymatic activities in the cell membrane.

Phosphatidylethanolamine methyltransferase and cAMP, cGMP phosphodiesterases in lymphocytes and monocytes in sarcoidosis

Among the various hypotheses proposed to explain immune cell defect in sarcoidosis, we examined thoroughly that of Faguet who described abnormalities of signal transmission at lymphocyte membrane level. Phosphatidylethanolamine methyltransferase and cAMP cGMP phosphodiesterases were studied in blood lymphocytes and monocytes from 8 subjects with sarcoidosis disease. Phosphatidylethanolamine methyltransferase (PMT1) plays an important regulatory role in membrane signal transmission. cAMP and cGMP phosphodiesterases (PDE) regulate cytoplasmic cyclic nucleotide levels and so participate in the modulation of the cell cycle. We observed a decreased PMT1 activity in lymphocytes and monocytes and a decreased cAMP and cGMP PDE activities in monocytes. It is not now possible to say if these abnormalities are primary or secondary. Whatever the origin of this dysfunctioning, these results evoke simultaneous disturbances of membrane signal transmission and cell cycle in monocytes and membrane abnormalities in lymphocytes. These abnormalities could explain some immune cell defects in sarcoidosis disease.

Cyclic AMP and cyclic GMP phosphodiesterase activities in Hodgkin's disease lymphocytes

Cyclic nucleotide phosphodiesterase (PDE) activities were studied in peripheral blood monocyte-depleted lymphocytes and enriched T-lymphocyte suspensions from thirteen patients with previously untreated Hodgkin's disease (HD) and fourteen age and sex matched healthy volunteers. Monocyte-depleted lymphocytes from HD patients showed PDE-activities which were two times higher than in their normal counterpart cells. The mean cAMP-PDE activity present in enriched HD T-lymphocyte suspensions was four times higher than in control T-lymphocytes, and the mean cGMP-PDE associated with HD T-lymphocytes was three times higher than in the controls. The hydrolytic activities present in both monocyte-depleted and T-lymphocyte enriched cells suspensions remained unchanged in absence or in the presence of calmodulin and calcium. Since depressed cAMP and cGMP resting levels have been observed in HD lymphocytes and lymphocyte subpopulations, our results suggest that the elevated PDE activities are, at least in part, responsible for the alterations in lymphocyte cyclic nucleotide levels.