Oral melatonin administration and programmed cell death of neutrophils, lymphocytes, and other cell types from rats injected with HL-60 cells

Recent years have seen mounting evidence for the role of melatonin in mediating programmed cell death, with a protective, anti-apoptotic effect in healthy cells, but an anti-tumoural, pro-apoptotic action in many tumour cells. In this study, we evaluated the effect of melatonin on the programmed cell death induced by thapsigargin (TG), on lymphocytes and neutrophils, and on various tissues obtained from rats injected with human promyelocytic leukaemia cells (HL-60), treated with melatonin in their drinking water (20 microm), and fed ad libitum. Melatonin treatment significantly reduced caspase-3 and -9 activity, and caused the proportions of lymphocytes, neutrophils, and eosinophils to revert to their basal values. No histological differences were observed. In conclusion, melatonin has anti-apoptotic effects on lymphocytes and neutrophils obtained from rats injected with HL-60 leukaemia cells.