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a Istituto di Chimica Biologica, Università di Urbino, Urbino, Italy b Dipartimento di Biologia, Università di Roma "Tor Vergata," Roma, Italy c Cattedra di Medicina del Lavoro, Università di Roma "Tor Vergata," Roma, Italy
Key Words: melatonin • pro-oxidant • reduced glutathione • ROS • glutathione peroxidase
Address for correspondence: Maria Cristina Albertini, Istituto di Chimica Biologica "G. Fornaini," Via Saffi, 2–61029 Urbino, Italy. Voice: +39-722-305288; fax: +39-722-320188. e-mail: cemetbio{at}uniurb.it
It was long believed that melatonin might counteract intracellular oxidative stress because it was shown to potentiate antioxidant endogenous defences, and to increase the activity of many antioxidant enzymes. However, it is now becoming evident that when radicals are measured within cells, melatonin increases, rather than decreasing, radical production. Herein we demonstrate a pro-oxidant effect of melatonin in U937 cells by showing an increase of intracellular oxidative species and a depletion of glutathione (GSH). The activity of glutathione peroxidase is not modified by melatonin treatment as it does occur in other experimental models.
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