In vitro and in vivo protection by melatonin against the decline of elongation factor-2 caused by lipid peroxidation: preservation of protein synthesis.

As organisms age, a considerable decrease in protein synthesis takes place in all tissues. Among the possible causes of the decline of translation in old animals are the modifications of elongation factor-2 (eEF-2). eEF-2 occupies an essential role in protein synthesis where it catalyzes the ribosomal translocation reaction. eEF-2 is particularly sensitive to increased oxidative stress. However, all oxidants do not affect eEF-2, only compounds that increase lipid peroxidation. As peroxides are unstable compounds, they decompose and generate a series of highly reactive compounds, including aldehydes malondialdehyde (MDA) and 4-hydroxynoenal (HNE). We have previously reported that hepatic eEF-2 forms adducts with low-molecular weight aldehydes, MDA and HNE. Therefore, the protection of eEF-2 must be specifically carried out by a compound with lipoperoxyl radical-scavenging features such as melatonin. In this article, we show the ability of melatonin to protect against the changes that occur in the eEF-2 under conditions of lipid peroxidation induced by cumene hydroperoxide (CH), a compound used experimentally to induce lipid breakdown. As experimental models, we used cultured cells and rats treated with this oxidant compound. eEF-2 levels, adduct formation of this protein with MDA and HNE, and lipid peroxides were determined. In the cultured cells, protein synthesis rate was also measured. Our results show that melatonin prevented the molecular changes in eEF-2 and the decline in protein synthesis rate secondary to lipid peroxidation. The results also show that serum levels of several hormones were affected by CH-induced oxidative stress, which was partially or totally prevented by melatonin.