The role of toll-like receptors in the protective effect of melatonin against doxorubicin-induced pancreatic beta cell toxicity

Aims: Doxorubicin, an anticancer drug, has a toxic effect on many tissues such as heart, pancreas, liver, kidney, and testis. The aim of current study is to investigate whether melatonin would be protective in doxorubicin-induced beta (beta) cell toxicity via HMGB1/TLR2/TLR4/MAPK/NF-kappa B signaling pathway. Main methods: Human pancreatic beta cell (1.1B4) was used in the present study. Four experimental groups were created as control, melatonin (10 mu M), doxorubicin (2 mu M) and the combination of melatonin with doxorubicin. Following 24-h treatment, Mitogen-activated protein kinase (MAPKs), Toll like receptors (TLRs) including TLR2 and TLR4, pro-and anti-apoptotic protein expression levels were determined by western blotting. Total antioxidant (TAS), oxidant status (TOS) and oxidative stress index (OSI) of the cells as well as superoxide dismutase (SOD) levels were determined. Active caspase-8 activity was measured and TUNEL staining was performed to study apoptotic pathways. Mitochondrial membrane potential (MMP), some protein expressions and F-actin distribution were analyzed. Key findings: Doxorubicin caused to depolarize MMP, resulting in enhancing apoptosis by activation of caspase-8 via MAPKs/NF-kappa B pathway via elevation of TOS and decreasing TAS. Also, doxorubicin destroyed F-actin distribution and elevated TLR2 and some apoptotic proteins, including Bax. However, co-treatment of melatonin with doxorubicin could reverse depolarization of MMP and inhibition of apoptosis through MAPK/NF-kappa B signaling by decreasing TOS and increasing TAS. The co-treatment reversed the alternations of TLR2, TLR4, MAPKs and apoptotic protein expressions induced by doxorubicin. Significance: Melatonin could be a good candidate against pancreatic beta cell toxicity-induced by doxorubicin through TLR2/TLR4/MAPK/NF-kappa B pathways.