The influence of melatonin on apoptosis of human neutrophils

Abstract

Aim: Melatonin (Mel) besides its main role in circadian and seasonal rhythm coordination, plays a role in immunoregulation and inflammatory responses. The melatonin’s ability to modulate apoptosis is one of its important roles related to its effect on immune system but the exact effect of its action and the mechanisms of apoptosis control by melatonin remain still unclear. The goal of our study was to examine the involvement of melatonin in the apoptosis of human neutrophils in vitro and possible mechanisms of this action. Material/Methods: We measured the effect of melatonin on the spontaneous and TNF-α-induced apoptosis of human neutrophils using propidium iodide and Annexin-V and on caspase-3 activation, apoptosis-related surface antigen expressions, intracellular reactive oxygen species (ROS) generation and cytochrome c release using flow cytometry and commercial reagents. Results: Melatonin does not affect spontaneous apoptosis of human neutrophils and mitochondrial cytochrome c release but protects the cells from the significant rise of TNF-α-induced apoptosis and cytochrome c release. Intracellular ROS generation in PMA-stimulated neutrophils did not change after the influence of melatonin but the significant drop of ROS generation in neutrophils stimulated with TNF- α was upregulated to the control level after preincubation of the neutrophils with melatonin. Melatonin did not change significantly Fas, Fas-L and active caspase-3 expressions in neutrophils. Conclusions: Melatonin does not affect the spontaneous apoptosis, however, inhibits TNF-α-induced apoptosis of human neutrophils. Our findings suggest that the intrinsic pathway of the process is a result of the melatonin induced mitochondrial alterations.