The protective effect of exogenous
melatonin or 6-hydroxylmelatonin on neurons was examined in N2a cells following exposure to
oxygen-
glucose-serum deprivation insults. After N2a cells cultured in vitro were deprived of
glucose, serum and
oxygen for 90 min, the different concentrations of
melatonin or 6-hydroxylmelatonin were added to the medium. Then, treated cells were cultured for different intervals. At the end of the treatment, the collected culture
solution was used for the analysis of the activity of
lactate dehydrogenase (LDH) and the cells were used for the examination of the following parameters: cell viability (MTT), DNA fragmentation,
reactive oxygen species (ROS) production, mitochondrial transmembrane potential,
cytochrome C and
caspase 3 activity. The results show that
melatonin and 6-hydroxylmelatonin both reduced
oxygen-
glucose-serum deprivation-mediated N2a cell apoptosis, but they could not completely inhibit the apoptosis of the cells and the inhibitory effect of
melatonin was stronger than that of 6-hydroxylmelatonin. Both of them could inhibit LDH and
cytochrome C release and
caspase 3 activity. Although 6-hydroxylmelatonin could no longer maintain mitochondrial transmembrane potential 6 h after reperfusion, its inhibitory effect on
cytochrome C release from mitochondria and the scavenging role of ROS were stronger than those of
melatonin. Moreover,
melatonin promoted ROS production at the 15th min of the reperfusion, and then it began to remove ROS from cells. Our study showed that
melatonin and 6-hydroxylmelatonin can be used as supplements in the treatment of
neurological disorders involving oxidative stress.
Melatonin serves as more than a ROS scavenger and its other roles await further study.