Rapid and transient stimulation of intracellular reactive oxygen species by melatonin in normal and tumor leukocytes

RADOGNA, FLAVIA
Paternoster, L
DE NICOLA, MILENA
Cerella, C
Ammendola, S
Bedini, A
Tarzia, G
AQUILANO, KATIA
CIRIOLO, MARIA ROSA
GHIBELLI, LINA

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Publication date

January 2009

DOI

10.1016/j.taap.2009.05.012

Publisher

country:NL

Abstract

Melatonin is a modified tryptophan with potent biological activity, exerted by stimulation of specific plasma membrane (MT1/MT2) receptors, by lower affinity intracellular enzymatic targets (quinone reductase, calmodulin), or through its strong anti-oxidant ability. Scattered studies also report a perplexing pro-oxidant activity, showing that melatonin is able to stimulate production of intracellular reactive oxygen species (ROS). Here we show that on U937 human monocytes melatonin promotes intracellular ROS in a fast (<1 min) and transient (up to 5-6 h) way. Melatonin equally elicits its pro-radical effect on a set of normal or tumor leukocytes; intriguingly, ROS production does not lead to oxidative stress, as shown by absence of protein ...