Apoptogenic effect of fentanyl on freshly isolated peripheral blood lymphocytes

ackground: Opioids may trigger the apoptotic death of widely ranging cell types, and apoptosis contributes to the immune deficiency of critically ill patients and sub- jects experiencing surgical trauma. There is evidence that an altered mitochondrial membrane potential constitutes an early and irreversible step in the death-signaling pathway of apoptosis. This study investi- gated whether fentanyl, a opioid widely used in the management of these patients, may induce apoptosis of T cells by altering their mitochondrial membrane potential.Furthermore, recent studies have suggested that the tran- sient immune deficiency syndrome along with lymphocyto- penia commonly seen in the early postoperative period after surgical trauma could be dependent on the increased lympho- cyte commitment to apoptosis.4,5 This could be a crucial factor in the susceptibility of patients receiving opioids to septic complications, but the ultimate mechanism underlying such a loss of lymphocytes via apoptotic death in the imme- diate postoperative period has not yet been elucidated. In particular, it is not clear whether anesthetic drugs, in addition to surgical stress alone, could be directly implicated in this phenomenon. Fentanyl, one of the most widely used synthetic opioids for anesthesia procedures, duplicates the action of morphine as a opiate receptor agonist, but to the best of the authors’ knowledge, no study has yet investigated whether exposure to fentanyl interferes with the process of apoptotic cell death. Recent studies have demonstrated that mitochondria ac- tively participate in the central control or executioner phase of the cell death cascade.6,7 This crucial role of mitochondria in apoptosis modulation is reinforced by the results obtained from distinct approaches, establishing that mitochondria can contribute to programmed cell death via the production of cell death–signaling reactive oxygen species (ROS) such as su- peroxide anions, hydrogen, organic peroxides, and radicals. copy. Furthermore, production of reactive oxygen species, expression of the Fas-Fas L pro-apoptotic pathway, and apoptosis fre- quency were measured by means of flow cytometry. Control cells were incubated for the same times in the complete culture me- dium without the drug. Results: Flow cytometry analysis showed a significantly increased rate (p < 0.05) of lymphocytes with disrupted mitochondrial membrane potential after incubation with fentanyl for 90 and 120 minutes, as compared with both control cells and lymphocytes cultured in the presence of fentanyl for 60 minutes. In addition, as early as 60 minutes after exposure to fentanyl, cells displayed a disrupted mitochondrial membrane po- tential when this was assayed by meansMethods: Peripheral blood lympho- cytes were cultured in the presence of 30 ng fentanyl for 60 (time 1), 90 (time 2), and 120 (time 3) minutes, respectively. The cells then were processed for assessment of mitochon- drial membrane potential by means of flow cytometry and confocal scanning micros- of confocal laser scanning. These find- ings were associated with increased pro- duction of reactive oxygen species. The frequency of apoptotic lymphocytes was markedly increased (p < 0.05) after 120 minutes of incubation, as compared with untreated cells and cells exposed to fen- tanyl for only 60 and 90 minutes. Ex- pression of Fas-FasL was not substan- tially affected by exposure to fentanyl. Conclusions: Fentanyl may induce a time-dependent apoptosis of lymphocytes by altering their mitochondrial redox metabolism. Key Words: Fentanyl, Surgical trauma, Apoptosis, Programmed cell death, Criti- cally ill patient, Lymphocyte, Mitochondria, Mitochondrial membrane potential, Reac- tive oxygen species, Opioids.