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Updated: Aug 19, 2026

Monitoring Neutrophil Elastase and Cathepsin G Activity in Human Sputum Samples
Published on: May 21, 2021
Histamine up-regulates phosphodiesterase 4 activity and reduces prostaglandin E2-inhibitory effects in human
Objective:
To investigate whether histamine produces up-regulation of phosphodiesterase (PDE) activity with functional consequences in human peripheral blood neutrophils.
Methods:
PDE activity was studied by a radioisotopic method following anion-exchange chromatography. Reverse transcriptase-polymerase chain reaction (RT-PCR) was used for detection of mRNA transcripts of PDE4 subtypes. Cyclic AMP (cAMP) levels were measured by enzyme-immunoassay, and superoxide generation by cytochrome c reduction.
Treatment:
Neutrophils were incubated for 4 h with histamine (1 microM).
Results:
PDE4 was the only isoenzyme activity increased in treated neutrophils. Kinetic analysis showed a approximately 1.5-fold increase in Vmax without alteration of Km values. cAMP content in treated cells was higher than resting values (0.52+/-0.07 vs. 2.75+/-0.31 pmol/10(6) cells). RT-PCR showed increased expression of mRNA transcripts for PDE4B in histamine-treated cells. Functionally, up-regulation of PDE4 reduced the inhibition by prostaglandin E2 of zymosan-induced superoxide generation.
Conclusion:
Histamine up-regulates PDE4 activity and produces heterologous desensitisation of human neutrophils.
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