Proteomic identification of proteins differentially expressed by melatonin in hepatic ischemia-reperfusion injury

Hepatic ischemia-reperfusion (I-R) injury induces hepatic dysfunction or failure. Melatonin is a potent free radical scavenger and a strong antioxidant. Although many studies have demonstrated the protective effect of melatonin in hepatic injury, the molecular mechanisms of this protection are unclear. We identified specific proteins that are differentially expressed by melatonin treatment in hepatic I-R injury. Adult mice were subjected to 1 hr of ischemia and 3 hr of reperfusion. Animals were treated with vehicle or melatonin (10 mg/kg, i.p.) 15 min prior to ischemia and just before reperfusion. Serum aspartate aminotransferase and alanine aminotransferase levels were higher in I-R group than in sham-operated group, and these increases were reduced by melatonin treatment. Proteins that were differentially expressed following melatonin treatment during hepatic I-R injury were detected using two-dimensional gel electrophoresis. Hepatic I-R injury induced down-regulation of glyoxalase I, glutaredoxin-3, spermidine synthase, proteasome subunit beta type-4, and dynamin like protein-1 (DLP-1). However, melatonin prevented the reductions in these proteins induced by I-R injury. Among the identified proteins, we focused on DLP-1, which is essential for the maintenance of mitochondrial and endoplasmic reticulum morphology. Western blot analysis confirmed that melatonin prevents the hepatic I-R injury-induced decrease in DLP-1. These results suggest that melatonin protects hepatic cells against hepatic I-R injury and that its protective effects involve the regulation of specific proteins.