The protective effect of melatonin on benzo(α)pyrene-induced hepatotoxicity in mice

Benzo(a)pyrene [B(a)P] is a polycyclic aromatic hydrocarbon which is considered as a widespread pollutant. In the B(a)P metabolic pathway, the generation of highly reactive compound and oxygen free radicals cause to oxidative damage of macromolecules, tissue destruction, apoptosis and cell death in vital organs such as brain, heart and liver.Melatonin, a circadian hormone secreted by the pineal gland, exerts various biological activities such as antioxidant and anti-apoptosis on liver damage caused by various diseases. In addition, it is proposed that the administration of melatonin influences the autophagy pathway which is known as one of the critical cellular homeostatic mechanisms. Many studies have shown that autophagy exerts protective effects on liver damage and melatonin exhibits hepatoprotective properties. This study was aimed to evaluate the protective role of melatonin on B(a)P-induced hepatotoxicity through its effect on the autophagy and apoptotic pathway.Materials and Methods: Forty Male BALB/c mice were divided into four groups and treated for 28 days; group I (B(a)P + melatonin solvent, oral gavage and intraperitoneally (i.p.), respectively), group II (B(a)P 75 mg/kg, oral gavage), group III (B(a)P 75 mg/kg, oral gavage + melatonin 20 mg/kg, i.p.), group IV (melatonin 20 mg/kg, i.p.). Malondialdehyde (MDA) and reduced glutathione (GSH) contents were determined in liver. Western blot analysis was conducted to investigate the expression of hepatic LC3 II/I, Beclin1, Caspase-3, BAX/Bcl2, BCL2/Adenovirus E1B 19 kDa Interacting Protein 3 (BNIP3) and Sirtuin 1.Results: Mice treated with B(a)P showed a marked increased MDA and reduced GSH which inverse by melatonin administration. Western blot analysis indicated that the expression level of caspase-3, Bax/Bcl2 and BNIP3 were upregulated and the expression level of LC3 II/I, Beclin1 and Sirtuin 1 were downregulated due to B(a)P administration (75 mg/kg), suggesting the activation of apoptosis cell death and inhibition of autophagy pathway. Concurrently administration of melatonin (20 mg/kg) with B(a)P reduced the apoptotic markers and elevated the autophagic proteins.Conclusion: These findings suggest that the apoptosis signaling pathway may involve in B(a)P-induced hepatotoxicity in mice liver and melatonin significantly reduced B(a)p hepatotoxicity. Melatonin afforded hepatoprotection through sirtuin 1-mediated autophagy signaling.

Keywords:

Benzo(α)pyrene , Melatonin , Hepatotoxicity , Apoptosis , Autophagy , Sirtuin1