Abstract
Background: It has been shown that cells of the immune system release opioid peptides and possess receptors for them. The concentrations of opioid peptides in the peripheral circulation rapidly increase during inflammation and acute stress response.Aims: The effect of opioid peptides Met-enkephalin (M-ENK) and beta-endorphin (β-END) on the oxidative metabolism of normal human neutrophils and their death by apoptosis in vitro was investigated.Methods: Isolated from peripheral blood, neutrophils were incubated in the presence or absence of 10-6 to 10-10 M of M-ENK and β-END for 12 and 18 h. Apoptosis of neutrophils was determined in vitro by flow cytometric analysis of cellular DNA content and Annexin V-FITC protein binding to the cell surface. The MTT-reduction assay was employed to estimate the oxidative metabolism of neutrophils.Results: Treatment with M-ENK caused a significant increase in apoptotic cells after 18 h of culture: